Engine Petrol

69
1 ENGINEERING 475 SIC PETROL ENGINE TECHNICAL SPECIFICATION ENGINE Model : TATA 475 SIC - Carburetted Type : Water cooled carburetted type petrol Engine No. of Cylinders : 4 inline Bore/Stroke : 75 mm x 79.5 mm Capacity : 1405 cc Max. Engine Output : 60 PS at 5000 rpm Max. Torque : 105 Nm at 2500 rpm Compression Ratio : 9 : 1 Firing Order : 1-3-4-2 Engine oil capacity : 4 Litres Cooling system capacity : 6 Litres

description

TATA Manual del Motor

Transcript of Engine Petrol

1

ENGINEERING

475 SIC PETROL ENGINE

TECHNICAL SPECIFICATION

ENGINE

Model : TATA 475 SIC - Carburetted

Type : Water cooled carburetted type petrol Engine

No. of Cylinders : 4 inline

Bore/Stroke : 75 mm x 79.5 mm

Capacity : 1405 cc

Max. Engine Output : 60 PS at 5000 rpm

Max. Torque : 105 Nm at 2500 rpm

Compression Ratio : 9 : 1

Firing Order : 1-3-4-2

Engine oil capacity : 4 Litres

Cooling system capacity : 6 Litres

2

ENGINEERING

475 SIC PETROL ENGINE

LIST OF SPECIAL TOOLS

Sr. No. Description Part No.

1. Box spanner (16 A/F) for spark plug 2702 5890 06 01

2. Extended socket (10mmA/F) for oil sump mounting screw 2702 5890 06 03

3. Camshaft Locking Pin 2702 5890 06 04

4. Flywheel locking pin 2702 5890 06 05

5. Lock plate for camshaft gear washer 2702 5890 06 07

6. Drift for crankshaft oil seal in rear cover 2702 5890 06 08

7. Drift for removal / fitment of valve guide 2702 5890 06 11

8. Spacer for valve guide fitment 2702 5890 06 12

9. Drift for fitment of oil seal on valve guide 2702 5890 06 14

10. Valve spring compressor 2702 5890 06 15

11. Support rail 2702 5890 06 16

12. Drift for valve guide seal fitment 2702 5890 06 17

13. Spanner for carburettor fitment 2702 5890 07 01

14. Drift for oil pump oil seal 2702 5890 18 01

15. Spanner for oil filter 2702 5890 18 02

16. Bracket (LH) for mounting engine on stand 2702 5890 24 02

17. Bracket (RH) for mounting engine on stand 2702 5890 24 03

18. Engine repair stand 2573 5890 24 01

19. Drift for fitment of camshaft oil seal 2654 5890 05 08

20. Engine support stand 2702 5890 24 01

3

ENGINEERING

475 SIC PETROL ENGINE

TIGHTENING TORQUES :

The fasteners should be tightened to specified torque at recommended intervals (km). If various fasteners are nottightened to specified torques, that is either over tightened or let loose, it will result in leakage at joints anddamage to the parts/threads. It will also adversely affect the performance of the parts/systems as clearances/bearing plays in the aggregates are governed by the tightening torques of the fasteners.

When choosing the torque wrench, remember that it should not be subjected to torque exceeding three fourthsof its capacity. Before tightening, clean the threads and apply a little oil.

Serial Description Torque in mkg.No.

1. Main Bearing Cap bolt M10 x 1 5.5 #

2. Cylinder head bolts M10 x 1.1 3, 5, 7.5 (Ref. Note) #

3. Spark plug in cylinder head M14 x 1.5 2.5

4. Cylinder head cover bolts M6 1.0 #

5. Oil sump Screw M6 x 1 0.6 to 0.7 #

6. Sealing plug for oil gallery block rear M14 x 1.5 3.5

7. Oil sump drain plug M12 x 1.5 3.5

8. Rear timing cover to block M6 x 1 1.0

9. Rear timing cover to head cover M6 x 1 1.0

10. Timing belt cover M6 x 1 1.0

11. Rear cover crank case on cylinder block screw M6 x 1 1.0 #

12. Connecting rod cap Nut M9 x 1 5.25 #

13. Flywheel mounting screw M10 x 1 5.0 #

14. Crankshaft gear to crankshaft bolt M14 x 1 4+60 0 #

15. Vibration damper / 4 groove A/C pulley to crankshaft gear 2.5

16. Belt tensioner adjuster bolt M10 x 1.5 3.0

17. Cam thrust plate 1.0

18. Timing belt idler to cylinder block bolt M10 x 1.5 4.5 #

19. Camshaft gear to camshaft screw M12 x 1.25 8.0

20. Lock Nut (Rocker adjusting screw) M9 x 1 3.5

21. Assembly Fuel feed pump on cylinder head screw M8 x 1.25 2.0 #

22. Exhaust manifold mounting bolts on cylinder head M8 x 1.25 2.0 #

23. Starter motor on Transaxle bolt M8 x 1.25 2.4

24. Alternator bracket to cylinder crankcase M8 X 1.25 2.0

25. Alternator to bracket M10 2.0

26. Adopter to cylinder head Stud M6 x 1 2.0 #

27. Distributor to adopter stud M8 x 1.25 2.5

4

ENGINEERING

475 SIC PETROL ENGINE

Serial Description Torque in mkg.

No.

28. Alternator tensioner bracket to block M8 x 1.25 2.0

29. Alternator to tensioner bracket screw M8 x 1.25 1.5

30. Oil pump on cylinder block 1.0 #

31. Assembly Strainer to oil pump M6 x 1 1.0

32. Assembly oil filter to cylinder crankcase M12 x 1.5 Ref. Note @ #

33. Oil pressure switch on cylinder crankcase M20 x 1.5 3.0

34. Water pump to cylinder crankcase screw M6 x 1 1.0 #

35. Water outlet elbow to intake manifold Nut M6 x 1 1.0 #

36. Water inlet elbow to cylinder crankcase screw M8 x 1.25 2.0

37. Temperature Transducer on cylinder head M14 x 1.5 1.5

38. Water inlet elbow to intake manifold nut M6 x 1 1.0

39. Thermostat cover to intake manifold nut M6 x 1 1.0

40. Lifting hooks to cylinder head screw M8 x 1.25 2.5

41. Engine mounting bracket to block M10 x 1.5 4.5

42. Engine mounting bracket to arm 4.0

43. Power steering pump mounting on bracket screw M8 x 1.25 2.5

44. A/C Compressor bracket to cylinder block screw M8 x 1 2.5

45. A/C Compressor to A/C compressor bracket bolt M8 x 1.25 2.5

46. Power steering pulley to power steering pump Nut M12 x 1.25 8.0

47. Assembly Idler to Slider (A/C compressor belt tensioner) Nut M8 x 1.25 2.5

Tolerance on Torque values + 5% for those marked # and + 10% for others

Note @ Apply oil on seal face and screw in until seal touches face. Tighten further by 3/4 turn. Do not over tighten.

5

ENGINEERING

475 SIC PETROL ENGINE

PRELIMINARY INSPECTION OF ENGINE :

Before proceeding to carry out actual overhauling ofengine it is desirable to have a preliminary inspectionof engine to ascertain whether an engine overhaul isnecessary and to what extent.

Most common reasons for which engine is overhauledare :

1. Loss of power

2. Excessive engine oil consumption

3. Excessive low engine oil pressure

4. Mechanical failures

To know exact reason and general condition of engine,proceed as follows :

1. LOSS OF POWER

Loss of engine power may be due to :

a. Defective Ignition system

b. Defective Fuel system

c. Clogged air cleaner/choked exhaust silencer

d. Clutch slippage

e. Brake binding

f. Loss of engine compression

a. IGNITION SYSTEM

Check the distributor for proper functioning(Refer TVS Workshop Manual for details). Alsocheck the Spark plug for proper functioning.

b. FUEL SYSTEM

Check condition of fuel filter element, ignitiontiming (using stroboscope & flywheel markings),carburettor and fuel pump for properfunctioning.

c. CLOGGED AIR CLEANER/CHOCKED EXHAUSTSILENCER

Loss of power with unusual black smoke fromengine exhaust indicates lack of air or low aircharging pressure to carburettor.

Clean air cleaner. Check all joints for air leakage.If power loss with black smoke is still felt, checkexhaust silencer for choking. Clean and replacesilencer if necessary. Check air leakages in theinlet manifold.

d. CLUTCH SLIPPAGE

Clutch slipping can be confirmed by any of thefollowing two methods:

Drive the car in 1st and 2nd gear at maximumspeed corresponding to that gear. Withaccelerator pedal fully pressed, apply brakegradually with left foot. If the engine stalls, itmeans that clutch does not slip.

OR

Drive car with weight equal to GVW in 3rd gearon level ground and let the speed drop down toapproximately 15 kmph. Now press acceleratorpedal fully. With slipping clutch, the car speedwill not pick up and also clutch burning smell willbe noticed. If this does not occur and car picksup speed, it indicates that clutch does not slip.

e. BRAKE BINDING

During driving apply brakes number of times andthen shift gear to neutral position Check brakedrums for over-heating and if necessary jack upthe car and check wheels for free rotation.

f. CHECKING ENGINE COMPRESSION PRESSURE

1. If loss of power is not on account of defectivefuel system, lack of air, choked exhaust silencer,clutch slipping and brake binding. Check enginecompression as follows :

2. Warm up engine preferably by road drive to geta temperature of about 75 to 85 0C.

3. Remove all spark plugs.

4. Remove air cleaner filter element.

5. Install Compression gauge into one of the sparkplug hole.

6. Disengage clutch (to reduce starting load onengine) and depress accelerator pedal all theway to make throttle valve open fully, in additionto open secondary throtle valve normally.

7. Crank engine with fully charged battery, and readthe highest pressure on compression gauge.

8. Carry out steps 5 to 7 on each cylinder to obtaincompression pressures. The specifiedcompression pressure is 9.5 bar min.

9. Variation in compression pressure betweencylinders should not be more than 0.5 bar.

6

ENGINEERING

475 SIC PETROL ENGINE

8. Refill the weighed oil into the oil tank. Do notspill any oil. The vessel used for draining shouldnot be used for any other purposes.

9. Drive the vehicle approx. 200 - 300 km. This driveshould include at least 30 - 40 kms. of highwayor similar road, vehicle running at about 60 kmph.Let this drive distance be ‘D’ kms.

10. Immediately after the test drive, place the vehicleat the same spot from where it started.

11. Now place the same previously used vesselbelow the oil tank, unscrew the drain plug anddrain off oil into the vessel. Drain the tank fully.

12. Weigh the vessel along with oil, now for thesecond time. Let this weight be ‘w2’ gms.

13. Find out standard oil consumption as -

Std. oil consumption =

(w1 - w2)(wt. of oil consumed, gms) x 1000

‘C’ (litres/1000km) sp. wt. of oil (gm/cm3) x ‘D’ (drive dist. in km.)

‘C’ =w1 - w2

litres/1000km0.88 x D

3. EXCESSIVE LOW OIL PRESSURE

Check the following :

a. External leakages.

b. Oil level in sump upto maximum mark ondipstick.

c. Oil pressure transducer for proper functioning.

d. Functioning of pressure relief valve on oil pump.

e. Oil pump performance

If oil pressure is found to be less than 2.8 bar atmaximum speed and 1.2 bar at idling speed. This maybe due to improper functioning of oil pump or defectin oil pump relief valve.

If low oil pressure is not on account of above factors,wear of journals/bearings is indicated for whichoverhaul of engine may be considered.

Checking oil pressure :

Procedure for checking

Before conducting the test ensure :

1. Engine oil level is at high mark on dipstick,otherwise top up.

2. No leakage.

3. Correct grade of engine oil is used.

10. Low compression pressure may be due toleakage past valves / piston rings/blown cylinderhead gasket. To ascertain the point of leakage,spray small quantity of clean engine oil in tocylinder showing low pressure and re-checkcompression pressure. If it improves, wear inpiston rings/cylinder bore is indicated. If it doesnot, leakage past the valves is indicated. Ifcompression pressure of adjacent cylinder is alsoon lower side, it may be due to blown cylinderhead gasket.

2. EXCESSIVE ENGINE OIL CONSUMPTION

High engine oil consumption may also lead tooverhauling of the engine but before proceeding tooverhauling, check following points :

1. Make sure that there is absolutely zero externalleakage of the oil (i. e. from the camshaft oil seal,crankshaft oil seal, oil sump gasket, oil pumpgasket, cylinder head cover gasket etc.

2. Ensure that oil separator in the cylinder headcover is properly mounted.

3. If no external leakage is found, determine theexact engine oil consumption, as per followingprocedure.

DETERMINING EXACT ENGINE OIL CONSUMPTION :

CAUTION :

Do not make a rough estimate of engine oil consumptionby noting the kilometers covered by the car at any randomstage and finding oil consumed from the topped upposition taking into consideration dipstick level andoil tank capacity.

PROCEDURE :

1. Once it is doubted that engine oil consumptionis higher, place the car on level ground.

2. Top up oil sump to its capacity of 4 litres.

3. Warm up the engine so that oil temperature is75 - 800 C.

4. Now take a clean vessel, place it below the drainplug of oil tank.

5. Drain the hot oil into the clean vessel. Drain itfully.

6. Screw in oil sump drain plug and tighten it.

7. Weigh the vessel along with oil let this weightbe ‘w1’, gms.

7

ENGINEERING

475 SIC PETROL ENGINE

Remove electrical connection from oil pressuretransducer.

Remove oil pressure transducer from cylinder block.

Install Oil pressure gauge in place of oil pressuretransducer.

Start engine and warm it up to normal operatingtemperature.

Warm up the engine and measure oil pressure. Itshould be within specified limits.

After checking oil pressure, stop engine and removeoil pressure gauge.

Before reinstalling oil pressure transducer, be sure toapply sealant on screw threads and tighten transducerto specified torque.

Tighten oil pressure switch to 1.2 - 1.5 mkg torque.

ENGINE VACUUM

The engine vacuum that develops in the intake line isalso an indicator of the condition of the engine. Thevacuum checking procedure is as follows :

1. Warm up engine to normal operatingtemperature. (Coolant temperature 75 0C-85 0C)

2. Set idle such that CO is 1% maximum (for carfitted with catalytic converter) & 3 % maximum(for car not fitted with catalytic converter).

3. Disconnect vacuum hoses from connection totank pressure relief valve side on intake manifold(near 3rd cylinder) and connect the special tool(Vacuum gauge and vacuum gauge hose joint)to the hose disconnected.

4. Run engine at specified idle speed and readvacuum gauge. Vacuum should be withinfollowing specification.

Vacuum 48 to 50 cm of Hgat 800 + 50 rpm.

5. After checking, remove the hose joint and thevacuum gauge, and connect the vacuum hose toTank pressure relief valve.

4. MECHANICAL FAILURES

Metallic knocking sound from an engine may be dueto faulty ignition, excessive clearance in main and bigend bearings, small end bush, tappets, piston slap,seizing of piston rings, scored cylinder bore orbreakage of any moving parts.

Fig.1

Defective alternator can also be a source of mechanicalnoise. Defect can be located by replacing alternatoror power steering pump (if fitted) or AC compressor(if fitted) or belt tensioner pulley with a new one.

Dismantling of engine may be considered if still noiseoccur even after attending all above mentionedproblems.

5. ENGINE ANALYSER

The Petrol Engine performance parameters can bechecked by commercially available Engine diagnosticequipment.

REMOVAL OF 475 SIC ENGINE FROM THE CAR :

Remove bonnet

Disconnect electrical cable connections for :l Batteryl Starter motorl Alternatorl Distributorl HT Coil (at HT coil end) Fig 1l FICD Solenoid ( if fitted )l Oil pressure switchl Water temperature transducerl Electric fan transducerl Reversing switch

Disconnect cables for Accelerator, Speedometerdrive, Clutch and Choke.

8

ENGINEERING

475 SIC PETROL ENGINE

Disconnect pipe lines from :

l Inlet manifold to vacuum booster

l Carburettor to canister.

l Carburettor fuel supply line.

l Carburettor to fuel return line.

Disconnect exhaust pipe from exhaust manifold

Drain coolant from cooling system

Disconnect hoses from and to radiator and heater coil.

Disconnect pipe from radiator to auxilliary tank andcylinder head to aux. tank.

Remove AC pipe lines (if AC is fitted)

Remove following sub assemblies :

l Air filter

l Clutch slave cylinder.

l Gear shift linkages from transaxle Fig. 2

l Radiator (if required)

Drain transaxle oil. Fig. 3

Remove drive shafts (for procedure, see suspensiongroup)

Fix chain to front and rear engine lifting hooks andhold chain in position with crane. Fig. 4

Unscrew and remove nut on ‘B’ mount bracket. Fig. 5

Remove ‘A’ mount support arm. Fig. 5

Remove ‘C’ mount bracket. Fig. 5

Lift engine slightly on car with the help of crane.

Place support stand under the engine & lower theengine along with transaxle assembly.

Remove the chain.

Fig. 3

Fig. 4

Fig. 5Fig. 2

�A� MOUNT

FRONT

�B� MOUNT

�C� MOUNT

2702 5890 24 01

9

ENGINEERING

475 SIC PETROL ENGINE

Lift the front end of the car till the engine is clear. ( It isrecommended to use two pole hoist to lift the car.)Remove the engine alonwith transaxle.

Remove starter motor.

Disconnect transaxle Assembly from engine. (Ref.transaxle group)

Remove alternator and its mounting bracket.

Mount the engine on work stand with mountingbracket Pt. No. 2702 5890 24 02 & 2702 5890 2403

Drain engine oil. Fig. 6

INSTALLATION OF ENGINE ON THE CAR :

l Check engine mounting pads for wear. Replacethem if necessary.

l Install the engine in reverse sequence of removal

l Tighten engine mounting bolts to specifiedtorque

l Connect all pipes, hoses and electricalconnections

l Fill specified quantity of oil in engine ofrecommended brand. Fig. 7

l Fill coolant in the cooling system through aux.tank

l Crank the engine momentarily. Let oil and coolantcirculate through the system. Remove airtrapped in cooling system with the air ventingscrew provided on outlet hose from cylinderhead to radiator top.

Confirm weather engine oil pressure indicator light isswitching off when engine is started.

l Check for leakage, rectify if any.

l Top up coolant upto FULL mark in auxiliary tank,if necessary.

REMOVAL OF RADIATOR FROM CAR

(Front bumper, Splash guard already removed - Forprocedure refer Body group of this manual)

1. Drain the coolant.

2. Remove all the hose connections i. e.

i. From the thermostat

ii. From the auxilliary tank.

iii. To the outlet elbow.

3. Disconnect the electrical connections,

i. To the condenser fan (In case of PLE & PLX)

ii. To the temperature sensor of cooling fan.

4. Unscrew the 2 M8 bolts & remove the radiatorbottom mounting member along with theradiator. Fig 8

Fig. 6

Fig. 7

Fig. 8

ENGINE OIL

DRAIN PLUG

ENGINE OILFILTER

1. ASSY. RADIATOR COMPLETE

2. CROSS MEMBER RADIATOR MOUNTING

3. RUBBER GROMET

1.

2.

3.

10

ENGINEERING

475 SIC PETROL ENGINE

SPECIFICATIONS

Leakage testing pressure : 1.5 bar

Auxillary Tank Cap Fig. 9

Pressure valve opening : 1 barVacuum valve opening : 0.05 bar (max)(suction)

INSPECTION

Check radiator for damages / leakages. Straightenbent fins if any.

CLEANING

Clean radiator frontal cores.

Installation :

1. Fit the radiator along with the radiator bottommounting member on to the car & tighten themounting bolts.

2. Fit back the 3 hose connections.

3. Connect the electrical connections fortemperature sensor & condenser fan (In case ofPLE & PLX models)

Fill coolant (clean water blended with anti freeze agentas per recommendation).

Top up coolant through auxiliary tank cap upto ‘Full”mark.

Fit Auxillary tank cap.

Run engine for short duration and top up coolant ifnecessary. Remove the trapped air though ventingscrew.

Bleeding procedure for cooling system :

(For refilling or during reconditioning after completedraining )

a. Fill coolant from the auxilliary tank (50 : 50mixture of soft water and antifreeze agent) afterensuring all the hoses are secured and leak proof.

b. During filling, keep the bleeding screw (on thehose from cylinder head to radiator) loose.

c. During coolant filling, ensure that the air in thesystem is removed from this bleeding screw andonly then tighten the screw, using a screwdriver.

d. Start the engine & slowly raise the engine speed& wait for the temperature to reach 850 C to 900

C to allow the thermostat to open up. Enginerunning at idling speed, open the bleedingscrew by using a screwdriver to allow any

Fig. 9

Fig. 10

trapped air in the system to escape. Tighten thebleeding screw & top up with coolant to max.level.

ALTERNATOR / POWER STEERING PUMP BELT

Removal :

l Loosen alternator top mounting screw andbottom mounting bolt Fig. 10

l Slightly loosen banjo bolt connections on vacuumpump

l Reduce alternator belt tension by loosening oftension adjusting nut (fig 11) or by pushingtowards engine.

l Remove alternator belt.

AUXILLIARY TANK CAPAUXILLIARY TANK

ENGINE WITH PULL TYPE ALTERNATOR BELTTENSIONING ARRANGEMENT

TOP MOUNTING SCREW

BOTTOM MOUNTING BOLT

11

ENGINEERING

475 SIC PETROL ENGINE

Inspection :

l Inspect alternator belt for wear, cracks and signsof failure. Replace, if necessary.

Fitment :

l Install alternator belt over crank shaft andalternator pulleys

l Pull alternator away from engine for specifiedtension & tighten the nut to specified torque.

l ALTERNATOR BELT TENSION IS CORRECT IF IT CANBE DEPRESSED BY 10-11 mm (for engine withalternator) & 8-9 mm (for engine with A.C.Alternator and Power steering) WITH THUMBPRESSURE (1O KG APPROX.) APPLIED IN THEMIDDLE OF ITS LENGTH Fig. 11 & 12

l Tighten alternator top mounting screw andbottom mounting bolt.

l Tighten banjo bolt connections on vacuum pump

A.C. COMPRESSOR BELT

REMOVAL

1. Loosen belt tensioner bolt. (Fig. 12) on idler /tensioner.

2. Release tension load on the belt and remove thebelt from the pulleys.

INSPECTION

1. Inspect the A. C. compressor belt for wear cracks,and signs of failures. Replace if necessary.

2. Inspect pulley grooves.

FITMENT

1. Install the belt over crankshaft and A. C.compressor pulleys.

2. Press the tensioner againsts the belt and tightthe tension bolt to specified torque.

3. Check belt tension.

4. A. C. Compressor belt tension is correcrt if it canbe depressed by 8-9 mm with thumb pressureapplied in the middle of its length betweencompressor and crankshaft pulleys.

Fig. 11

Fig. 12

ENGINE WITH SCREW & NUT TENSIONINGARRANGEMENT

BELT

ALTERNATOR

TENSIONER BRACKET(ON BLOCK)

TENSIONER

ALTERNATORFLANGE

LOCK NUT

TENSIONADJUSTINGNUT

ENGINE WITH A.C. ALTERNATORAND POWER STEERING PUMP

TENSIONER

BELT TENSION ADJUSTING SCREW

BELTTENSIONERROLLER

A. C. COMPRESSOR

12

ENGINEERING

475 SIC PETROL ENGINE

TIMING BELT :

Removal :

Remove alternator and / or AC belt

Unscrew the mounting screws & remove front timinggear train cover. Fig. 13

Keep crank shaft rotating with socket spannersimultaneously pressing camshaft timing pin till it lockscamshaft. Fig. 14

Check at this position whether timing pin2702 5890 0605 in crankcase locks the flywheel or not.Fig. 15

Fig. 14

Fig. 15

Fig. 13

13

ENGINEERING

475 SIC PETROL ENGINE

Fig. 16

Fig. 17

Remove timing pin locking the camshaft & now ensurethat flywheel is in locked position.

Fit lock plate for camshaft gear washer on cylinderhead as shown in Fig.16

Slacken the camshaft gear fixing bolt.

Slacken the mounting bolt of belt tensioner rollerassembly and rotate the belt tensioner in anticlockwisedirection to loosen the belt. Fig. 17

Remove timing belt.

Inspection :

Check belt in detail. If following flaws are evident,replace belt with new one.

l Back surface glossy, non elastic and so hard thateven if finger nail is forced into it, no mark isproduced.

l Cracked back surface rubber

l Cracked or exfoliated canvas

l Cracked tooth bottom

l Side of belt cracked

l Side of belt badly worn

l Badly worn teeth

l Missing tooth

NOTE :

Normal belt should have clear cut sides, as if cut witha sharp knife.

In initial stage of wear, load side tooth flank will looklike fluffy canvas fibre, rubber gone and colourchanged to white.

In last stage of wear, canvas on load side tooth flankwill be totally worn out exposting rubber.

Fitment :

Ensure that timing pin is in flywheel locked position.

Check that the cam gear is “Just” freely rotating on thecamshaft with mounting bolt in hand loose condi-tion.

Slacken all valve tappet clearance setting screws tosuch an extent that the screw bottom radius is justriding on the valve tips & tighten the locknuts.

NOTE :

This is to reduce the valve spring load on Camshaft,while rotating the camshaft.

Using appropriate spanner on camshaft gear fixing

bolt, rotate camshaft in clockwise direction with tim-ing pin placed on the cylinder head reference hole,until the camshaft is locked in timing position.

Slacken the fixing bolt so that the camshaft gear is“Just” freely rotating on camshaft. Fit the camshaft gearwasher lock plate as shown in Fig. 16

Check now that both the fly wheel and camshaft arein locked in timing position.

Fit timing belt on Crank shaft gear, water pumptensioner roller and camshaft gear.

Adjust the timing belt tension, by rotating tensionerroller clockwise and tighten the mounting screw, whiletightening the mounting screw ensuring that thetensioner roller does not rotate further in clockwisedirection. This will prevent overtensioning of timingbelt.

14

ENGINEERING

475 SIC PETROL ENGINE

Tighten the cam gear fixing bolt to a lower tighteningtorque of 1 mkg.

Remove cam shaft timing locking pin.

Re-tighten the cam gear fixing bolt to the specifiedtorque.

Remove camshaft gear washer lock plate and fly wheellocking pin.

Set valve tappet clearance on the following rockerarms. Fig. 18

Inlet - 1 & 2 and Exhaust - 1 & 3

Rotate crank shaft in clockwise direction by onerevolution and lock the fly wheel.

Set the valve tappet clearance on the reamainingrocker arms i. e.,

Inlet - 3 & 4 and Exhaust - 2 & 4

Rotate crankshaft in clockwise direction by morerevolution and check whether fly wheel and camshaftare in locked timing position.

NOTE :

In this procedure timing pin locking the camshaft isremoved from the cylinder head timing referencehole, whenever camshaft is subjected to very highlooserning and tightening torque through the gearfixing bolt. This is to prevent severe damage to cylin-der head, camshaft timing slot and subsequent prob-lem of very low oil pressure (due to increased bear-ing clearance on bearing No. 5 of cylinder. head).

Special ‘C’ tool should be used whenever cam gearfixing bolt is to be tightened or loosened.

Never use the timing pin in locked timing position tohold the camshaft during tightening or looseningprocess.

CYLINDER HEAD : (Engine on workstand)

Disassembly:

Remove electrical cable connections for :

l FICD

l Water temperature transducer

l Distributor Fig. 19

Remove

l By pass line Fig. 20Removel Spark plug leads from spark plug

Fig. 18

Fig. 19

Fig. 20

15

ENGINEERING

475 SIC PETROL ENGINE

Fig. 23

Fig. 24

Fig. 25

Fig. 21

Fig. 22

l Vacuum timing advance connection fromdistributor Fig. 21

l Distributor Fig. 22

l Distributor mounting adaptor from cylinder headFig. 23

l Fuel pipe line from fuel pump outlet connection

l Carburettor Fig. 24

l Intake manifold Fig. 25

16

ENGINEERING

475 SIC PETROL ENGINE

Fig. 28

Fig. 29

Fig. 30Fig. 27

Fig. 26

l Exhaust manifold Fig. 26

l Fuel return line from carburettor to fuel tank.

l Fuel pump Fig. 27

l Cylinder head cover Fig. 28Insert fly wheel locking pin and loosen camshaft gearmounting bolt. Fig. 29Also removel Timing beltl Dip stick clamping screwUnscrew and remove cylinder head mounting screwsin reverse order of tightening Fig. 30Slightly lift cylinder head to clear locating hollowdowel in crank case and remove it.

17

ENGINEERING

475 SIC PETROL ENGINE

l Cam shaft gear Fig. 31

l Rocker arm shaft locking grub screws and rockerarm shafts. Fig. 32 & 33

NOTE :

1) To ease the dismantling of rocker shaftrelieve the valve spring load by slackeningthe tappet setting screws. In this conditiondo not attempt to rotate the cam shaft, if youdo so valve tips will be damaged.

2) While pulling out Rocker arm shafts, take outthe rocker arm with springs & spring seatscarefully one by one.

l Remove Spark plugs Fig. 34

SPARK PLUG

Spark Plug - Champion

Spark Plug no. - C9YC

Spark Plug Gap - 0.7 mm to 0.8 mm

You should inspect the spark plugs periodically forcarbon deposits. When carbon accumulates on thespark plug, a strong spark will not be produced.Remove carbon deposits using a spark plug cleaner.

Spark Plug Replacement :

1. Clean up any dirt or oil that is collected aroundthe spark plug caps.

2. Pull out the spark plug cables by gripping at theconnector.

Fig. 31

Fig. 32

Fig. 33

Fig. 34

18

ENGINEERING

475 SIC PETROL ENGINE

3. Remove the spark plug with the help of boxspanner 2702 5890 06 01

4. Check and adjust the gap, it should be 0.7 mmto 0.8 mm. Fig. 34a

5. Replace the spark plug if the gap is more than0.8 mm.

6. Fix the spark plug and tighten it to the specifiedtorque (dry.)

7. Fit the spark plug cable.

Repeat the procedure for the other spark plugs.

Tighten the spark plug carefully. Overtightening candamage the threads in the cylinder head. A loose sparkplug can effect combustion and cause engine damage.

SPARK PLUG DEFECTS

The condition of spark plug firing ends can act as aguide to the state of tune and general condition ofthe engine.

The examples shown below are assumed to be thecorrect grade of engine.

NORMAL Fig. 35

Core nose lightly coated with grey-brown deposits.Electrodes not burning unduly - gap increasing about0.01 mm per 2000 km (with the use of unleaded fuel).Spark plugs ideally suited to engine.

HEAVY DEPOSITS Fig. 36

Possible causes : Fuel or oil additives. Oil in combustionchamber. Worn valve guides. Unvarying speed(stationary engine). Replace spark plugs.

CARBON FOULING Fig. 37

Characterised by dull black sooty deposits althoughunleaded fuel carbon fouling can appear as glossydeposits similar in appearance to oil fouling. Depositscan short circuit the firing end; weakening oreliminating the spark. check for : Over-rich mixturesetting, faulty choke mechanism or clogged air filter.Replace spark plugs.

Fig. 34a

Fig. 36

Fig. 37

Fig. 35

19

ENGINEERING

475 SIC PETROL ENGINE

OIL FOULING Fig. 38

Deposits can short-circuit the firing end, weakeningor eliminating the spark. May be caused by worn valveguides, bores or piston rings, or whilst a new oroverhauled engine is running-in. Cure the oil problem,if possible. Temporary use of the next hotter grade ofspark plug may stop the misfire. Replace spark plugs.

OVERHEATING Fig. 39

Likely causes are : Over-advance ignition timing.incorrect distributor advanced curve. Use of fuel withinsufficient octance rating. Weak misture. Discard sparkplugs showing signs of overheating, and cure thecause.

INITIAL PRE-IGNITION Fig. 40

Caused by serious overheating. Causes are those listedfor overheating but may be more severe. Correctivemeasures are urgently needed before engine occurs.Discard plugs in this condition.

SPLIT CORE NOSE Fig. 41

(May appear initially as a hair-line crack). Probablycaused by detonation waves, indicating : Over-advanced ignition timing. Incorrect distributoradvance curve. use of fuel with insufficient octancerating. Weak mixture. Manifold air-leaks. Coolingsystem problems. Incorrect gap setting technique.

Fig. 39

Fig. 40

Fig. 41Fig. 38

20

ENGINEERING

475 SIC PETROL ENGINE

Cylinder head disassembly continued

l Cyl. head cover mounting studs and spacer tubes.(replace if required) Fig. 42

l Cam shaft locking plate from cam shaft bearingcap at the front

Push the cam shaft from rear and pull out from front,with oil seal Fig. 43 & 44

Fit support rail, (2702 5890 0616) to cylinder headFig. 45

With spring compressor (2702 5890 06 15) compressvalve springs and remove valve lock halves Fig. 46

Remove valve lock retainers, valve springs, valve springseats and valves. Place them in correct sequence.

Fig. 43

Fig. 44

Fig. 45

Fig. 46

Fig. 42

21

ENGINEERING

475 SIC PETROL ENGINE

Mating Surface :

Using a straight edge and feeler gauge, check cylinderhead mating surface with crank case, Fig. 47 & 48.

If unevenness exceeds, replace cylinder head.

CYLINDER HEAD TOP AND BOTTOM SURFACEREMACHINING, IN SERVICE IS NOT PERMITTED.

Permissible unevenness of cyl. head Overall matingsurface (150 x 150) : cross wise 0.015 mm

length wise 0.030 mm.

VALVES

Check valve leakages by pouring gasoline on valvehead. Gasoline must not seep past valve seat.

Valves with burnt heads, excessive scoring and wearon stem should be replaced.

Check valve seat run out with respect to valve stem.Fig. 49. If it exceeds specified limit replace valve. Noattempt should be made to straighten bent valves. Ifvalve is free from any other defects except worn outseat, then only it can be rematched on valve grindingmachine as follows.

l Clamp valve on grinding machine jaws as closeas possible to valve head. Fig. 50

l Adjust grinding angle on graduated scale toachieve correct valve seat angle.

l Feed valve slowly towards grinding wheel untilwheel just touches valve head.

l Grind at low feed until valve seat is just clean allaround.

Fig. 48

Fig. 49

Fig. 50Fig. 47

INLET VALVE

A450

D

B

EXHAUST VALVE

C

B

AD

CC C

22

ENGINEERING

475 SIC PETROL ENGINE

Valve seat dimensions : Fig. 50

Fig. 51 Fig. 52

NOTE : After grinding, valve head thickness shouldnot be less than 0.85 mm.

VALVE GUIDES :

In case of valve stem sticking in valve guide before orexcessive clearance between them, remove valveguide from cylinder head using drift (2702 5890 0611)Fig. 51

INLET EXHAUST

Valve head dia. �A� mm 36.6/36.8 30.9/31.1

Valve seat angle 45 deg.+15' 45 deg.+15'

Valve stem dia �B� mm 6.97-0.015 6.96-0.015

Maximum run out of valve face with respect 0.2 0.2

to valve steam mm

Valve seat dia �C� mm 35 29.2

Valve seat end distance from valve face �D� mm 2.65+0.1 2.82+0.1

Maximum run out of valve seat with 0.030 0.030

respect to valve steam

Valve seat dia in cylinder head mm 34 28.0

Distance between cylinder head mating 14.4+0.05 14+0.05

surface with crank case to valve seat in

cylinder head mm

Maximum run out of valve seat in cylinder 0.030 0.030

head with respect to valve guide axis mm

Remove valve guide seals. Check condition andreplace if required with drift (2702 5890 0617) Fig. 52

Check valve guide bore diameter in cylinder head andif necessary, ream valve guide bore in cylinder headto next over size.

23

ENGINEERING

475 SIC PETROL ENGINE

Install matching size valve guide in cylinder head usingdrift 2702 5890 0611 and spacer, 2702 5890 0612.Fig. 53

Ream valve guide inside diameter to specified size.

Fit valve guide oil seals.

VALVE SEATS OF VALVES

Check valve seat height with respect to cylinder headmating surface. Replace valve seat inserts if they areworn out byond specified limit.

Cut exhaust and inlet valve seats with a 45 deg.cutter.Fig. 54

VALVE SEAT MUST BE ABSOLUTELY FAULTLESS ANDWITHOUT ANY CHATTER MARKS

If necessary lap valve seats to a smooth and even finishby using suitable hand pump grinder or a lappingpaste and valve itself.

Smear valve seat with carbon blue. Install valve in guideand turn it slowly under axial pressure.

CONTACT LINE ON VALVE SEAT MUST BE AROUNDENTIRE CIRCUMFERENCE AT EQUAL WIDTH

Distance between narrow diameter of valve face tocontact line should be minimum 0.5 mm

Check for leakages through valve seat by pouringgasoline on valve head. Gasoline must not seep pastvalve seat.

VALVE SEAT INSERTS :

For removing valve seat inserts from cylinder head usesuitable boring machine. Bore old insert thin (about0.5 mm thickness) and then pry it out.

Alternatively use a suitable turning tool to cut anannular groove into valve seat insert and then pull itout with a suitable puller. In order to avoid damaging

machined cylinder head mating surface with crankcase, place any soft protective sheet metal undersupports of puller.

Measure valve seat insert bore in cylinder head.

Fig. 54

Size Valve guide Valve guide Valve guide Valve guide

bore in cyl. head OD,mm ID,mm length, mm

Normal 12.99+0.008/-0.01 13.0 + 0.046 7 + 0.015

(Inlet) 39.5 (inlet) + 0.028 7

+ 0.016 (Exhaust) 46 (Exhaust)

Normal 1 13.09+0.008/-0.01 13.1 + 0.046 7 + 0.015

(Inlet) + 0.028 7

+ 0.016 (Exhaust)

Fig. 53

- 0

+ 0.004

- 0

+ 0.004

24

ENGINEERING

475 SIC PETROL ENGINE

If boring and prying is done carefully withoutdamaging valve seat insert bore in cylinder head,fitment of an over size valve seat insert will not benecessary.

Re-machined valve seat insert bore in cylinder headmust be exactly at right angle to cylinder head matingsurface with crank case. All specified dimensionsshould be strictly maintained to ensure properinterference of valve seat insert in its bore.

Clean valve seat insert and its bore in cylinder headthoroughly.

Just before installation :

l Place valve seat insert in mixture of Methanol anddry ice for about 20-30 minutes to bring its

temperature down to -150 deg. C.

l Heat cylinder head to approximately 80 deg. Cin water bath.

Install valve seat insert in cylinder head bore quicklyby using mallet.

Machine valve seat in cylinder head.

CAM SHAFT INSPECTION

Carry out visual inspection of cam shaft for :

l Overall heating of journals, which is indicated bybluish/brown colour

Fig. 55

l Deep scoring marks on journals and cam lobes

l Cracks, which should be checked on a magneticcrack detector.

Check hardness of cam shaft journals and cam lobes.It should be 40 HRC min.

Check cam shaft runout at 2nd, 3rd & 4th journal bysupporting it on V-block at 1st and 5th journal. Fig. 55

Check cam shaft journal dimensions.

Cam shaft journal & bearing bore dimensions (mm) :

Journal No. Cam shaft bearing journal Cam shaft bearingbore diameter in cylinder head journal diameter.

1 42.000 - 42.025 41.925 - 41.950

2 41.500 - 41.525 41.425 - 41.450

3 41.000 - 41.025 40.925 - 40.950

4 40.500 - 40.525 40.425 - 40.450

5 40.000 - 40.025 39.925 - 39.950

Maximum permissible run out of cam shaft bearing journal 0.025 mm

Maximum permissible axial play of cam shaft in installed condition 0.1/0.25 mm

Runout of oil seal mating diameter.

Valve seat insert :

Valve seat insert thickness

Inlet - 6.5 + 0.05 mm

Exhaust - 6.5 + 0.05 mm

Valve seat inside dia in insert

Inlet - 32 + 0.1mm

Exhaust - 26 + 0.1mm

25

ENGINEERING

475 SIC PETROL ENGINE

Valve seat insert & bore dia. in cyl. head

Stage Valve seat insert bore Valve seat insertdiameter in cyl. head (mm) out side diameter (mm)

INLET- Normal 38/38.03 38.13/38.155

- Normal 1 38.23/38.28 38.43/38.455

EXHAUST

- Normal 32.99/33.021 33.13/33.155

- Normal 1 33.29/33.321 33.43/33.455

Fig. 57

Cylinder head cover:

Remove the baffle plate in the cylinder head cover byremoving the screws. Fig. 55a.

Check the baffle plate gasket if it is torn/damage,replace if necessary otherwise it might result in highengine oil consumption.

Assembly of cylinder head :

Install valves in their respective positions

Install spring seat, valve springs and valve retainers.

Fit support rail (2702 5890 0616) on cylinder head

Fig. 56

With spring compressor, (2702 5890 0615), compressvalve springs and install valve lock halves Fig. 57

Smear cam shaft journals and cam lobes with molypaste grease Fig. 56

Fig. 55a

26

ENGINEERING

475 SIC PETROL ENGINE

Install cam shaft and lock it by lock plate at the frontFig. 58

Insert the rocker arm shaft with rocker arm spring andspring seat one by one CAREFULLY.

Rocker arm and rocker shaft dimensions:

Rocker shaft dia. :15 - 0.016 mm

Rocker bore dia. : 15 + 0.011 mm

CAUTION :

While inserting rocker arm shaft on inlet valves, ensurethat tapped hole on the shaft is at the front end andfor rocker arm shaft on exhaust valves the tapped holeon the shaft is at the rear end.

Check cam shaft axial play. It should be withinspecified limits Fig. 59

Check camshaft for rotation.

Fit camshaft oil seal with drift (Pt. No. 2654 5890 0508)

Fit camshaft gear and hand tighten the mounting bolt.

Measure piston projection above crank case andselect correct thickness of cylinder head gasket

PISTON GASKETPROJECTION THICKNESS,

mm mm

0.04 - 0.26 1.1

MAXIMUM DIFFERENCE BETWEEN PISTONPROJECTIONS OF ANY TWO PISTONS IN CRANK CASESHOULD NOT EXCEED SPECIFIED VALUE.

Ensure that cylinder head locating hollow dowel is inposition on crank case.

Ensure that timing pin 2702 5890 0605 is installed inposition. Fig. 60

Fig. 58

Fig. 60

Fig. 59

- 0.027

- 0.000

27

ENGINEERING

475 SIC PETROL ENGINE

Place cylinder head gasket of pre-determinedthickness.

Install cylinder head and tighten cylinder headmounting screws to 3 mkg torque in the correctsequence i.e. from centre to outwards. Then retightenscrews to 5 mkg torque in the same sequence - Thenloosen each screw by quarter turn and retighten to7.5mkg. torque. Fig. 61

Fig. 62

Fig. 63

1 2 3 4

10 6 2 3 7

9 5 1 4 8

Valve clearance adjustment.

VALVE CLEARANCES SHOULD BE CHECKED ONLY WHENENGINE IS COLD.

l Fit camshaft gear

Fitment :

Ensure that timing pin is in flywheel locked position.

Check that the cam gear is “Just” freely rotating on thecamshaft with mounting bolt in hand loose condition.

Slacken all valve tappet clearance setting screws tosuch an extent that the screw bottom radius is justriding on the valve tips & tighten the locknuts.

NOTE :

This is to reduce the valve spring load on Camshaft,while rotating the camshaft.

Using appropriate spanner on camshaft fixing bolt,rotate in camshaft in clock direction with timing pinplaced on the cylinder head reference hole, until thecamshaft is locked in timing position. Fig. 62

Slacken the fixing bolt so that the camgear is “Just”freely rotating on camshaft. Fit the camshaft gearwasher locking plate as shown in Fig. 63

Check now that both the fly wheel and camshaft arein locked timing position.

Fit timing belt on crank shaft gear, water pumptensioner roller and camshaft gear.

Adjust the timing belt tension, by rotating tensionerroller clockwise and tighten the mounting screw, while

Fig. 61

28

ENGINEERING

475 SIC PETROL ENGINE

tightening the mounting screw ensuring that thetensioner roller does not rotate further in clockwisedirection. This will prevent overtensioning of timingbelt.

Tighten the cam gear fixing bolt to a lower tighteningtorque of 1 mkg. Fig. 64

Remove cam shaft timing locking pin.

Re-tighten the cam gear fixing bolt to the specifiedtorque.

l Set the fly wheel and cam shaft in No.1 cylinderfiring position.

l Adjust the valve clearances of cylinder No. 1 & 2on inlet valves and cylinder No. 1 & 3 on exhaustvalves Fig. 65

l Remove the camshaft and crankshaft lockingpins.

l Rotate the crankshaft by one rotation in theclockwise direction and insert the flywheellocking pin.

l Adjust the valve clearances of cylinder No. 3 & 4on inlet valves and cylinder No. 2 & 4 on exhaustvalves Fig. 66

INLET EXHAUST

Specified 0.20 0.30

Fit,

l Spark plug. Fig. 67

Fig. 65

Fig. 66

Fig. 67Fig. 64

29

ENGINEERING

475 SIC PETROL ENGINE

l Adapter plate (distributor) with O ring (replaceif required)

l Distributor. CARE SHOULD BE TAKEN TO LOCATETHE LUGS ON THE DISTRIBUTOR SHAFT INTO THEOFFSET SLOT ON THE CAMSHAFT.

l Fuel pump with gasket

l Exhaust manifold Fig. 68

l Inlet manifold with gasket.Fig. 69

l Carburettor

l Spacer tube on cylinder head cover mtg. studs.

l Cylinder head cover along with camshaft gearrear cover. Replace the gasket if required.

l Timing belt gear cover. Fig. 70

Thermostat cartridge

l Thermostat cover with gasket

l Bypass line

l Dip stick clamp screw

Fill recommended quantity of oil.

CYLINDER BLOCK

(Cylinder head assembly removed)Disassembly

Uniformly and evenly unscrew clutch pressure platemounting screws and remove clutch pressure plateand clutch disc. Fig. 71

Fig. 69

Fig. 70

Fig. 71Fig. 68

30

ENGINEERING

475 SIC PETROL ENGINE

Remove :

l Vibration damper Fig. 72

l Crankshaft gear Fig. 73

l Water pump

l Timing belt tensioner

l Timing belt rear cover

l Oil filter by using spanner (2702 5890 1802)

Fig. 74

l Engine mtg. bkt. (intermediate)

l Oil sump by extended socket (2702 5890 0603)Fig. 75

l Oil pump strainer Fig. 76

l Oil pump

Fig. 74

Fig. 75

Fig. 76Fig. 73

Fig. 72

31

ENGINEERING

475 SIC PETROL ENGINE

Carefully remove combustion residues towards topend of cylinder bores, preferably by a broken pistonring or by ridge cutter.

Turn crank shaft and bring a pair of piston to BDC

Unscrew connecting rod bearing cap mounting nuts.Fig. 77

Remove connecting rod bearing caps with bearingshells.

Push these piston assemblies out of cylinders usingwooden handle of mallet.

Remove connecting rod bearing shells and duly markthem with paint on their backs in case these are to bereused.

IT IS ESSENTIAL TO ASSEMBLE CONNECTING RODBEARING CAPS TO THEIR RESPECTIVE CONNECTINGRODS

Verify serial numbers on connecting rod bearing capsand connecting rods.

Remove remaining pistons in same manner

Remove piston pin spring clips with suitable plier.

Fig. 78

Remove piston pins from piston by pushing them outusing soft drift. Fig. 79

Remove connecting rod

Fig. 77

Fig. 78

Fig. 79

32

ENGINEERING

475 SIC PETROL ENGINE

KEEP PISTON AND PISTON PIN IN SETS :

Insert flywheel locking pin. Fig. 80

Unscrew flywheel mounting screws Fig. 81

Remove flywheel locking pin.

Remove flywheel.

Unscrew and remove crankcase cover with oil seals.

Unscrew main bearing cap mounting bolts andremove main bearing caps. Fig. 82

Remove crank shaft main bearing shells and thrustwashers from crank case. Duly mark main bearingshells with paint on their backs, in case these are tobe reused.

Remove crankshaft Fig. 83

IT IS ESSENTIAL TO ASSEMBLE MAIN BEARING CAPS TOTHEIR RESPECTIVE POSITIONS IN CRANK CASE.

Fig. 80

Fig. 81

Fig. 82

Fig. 83

33

ENGINEERING

475 SIC PETROL ENGINE

Fig. 84

Remove piston rings from piston using ring expander.Fig. 84

Remove carbon deposits from piston

Clean piston and piston rings thoroughly

In case cylinder bore taper and ovality is withinspecified limit, then same piston and piston rings maybe reused.

Examine pistons for cracks, scoring, other damages,ring groove wear, piston pin bore wear, spring clipgroove wear/damage etc.

In case of any one piston with any one of this defect,complete piston set should be replaced.

Piston pin dia. 20.00/19.996 mmPiston Pin length 59.00/58.7 mmPiston Pin bore in piston 19.998/20.003 mmHeight of Piston 52.5 mmPiston to bore clearance 0.040 - 0.050 mmMax. permissible difference in weightsof pistons with pin & rings of an engine 3 gms.

PISTON AND PISTON RINGS :

Piston & piston bore sizes :

Stage Grade Cylinder bore Piston stampeddiameter mm diameter mm

A 75.00/75.01 74.96

Standard B 75.01/75.02 74.97

C 75.02/75.03 74.98

A R1 75.250/75.260 75.210

Repair I B RI 75.260/75.270 75.220

C RI 75.270/75.280 75.230

A RII 75.500/75.510 75.460

Repair II B RII 75.510/75.520 75.470

C RII 75.520/75.530 75.480

A RIII 75.750/75.760 75.710

Repair III B RIII 75.760/75.770 75.720

C RIII 75.770/75.780 75.730

PISTON RINGS :

Type of ring Axial clearance Butt clearancein piston groove in cylinder bore

1st Compression 0.03 / 0.07 mm 0.15 / 0.3 mmring

2nd Compression 0.02 / 0.06 mm 0.2 / 0.35 mmring

3rd Oil control - 0.2 / 0.6 mmring

34

ENGINEERING

475 SIC PETROL ENGINE

Fig. 88

Examine piston rings for scoring, lateral clearance inpiston ring groove and butt clearance in cylinder bore.Fig. 85 & 86

BUTT CLEARANCE OF PISTON RING SHOULD BEMEASURED IN UNWORN PORTION OF CYLINDER BORE.

In case of any piston ring with any one of this defect,complete ring set should be replaced.

When cylinder bores are re-bored or honed, pistonsand rings of appropriate size should be used.

Piston size is stamped on piston crown.

Install piston rings in their respective position onpiston using ring expander, with “TOP” marking upward.Fig. 87

Ensure that piston & rings are clean.

Assemble the expander of the oil ring in the 3rdgroove & then the bottom & top rails. Do not wind inthe rails on to the groove.

Assemble Taper compression ring in the 2nd grooveusing ring plier. Ensure ‘TOP’ marking is towards thepiston crown.

Assemble the Gas nitrided steel ring in the top grooveusing a ring plier. Stagger the ring gap.

Lightly oil the rings and use ring compressor, whileinserting into the cylinder.

CONNECTING RODS

Inspect connecting rod small end bush and ifnecessary, replace it.

Check connecting rod small end parent boredimension Fig. 88

Fig. 86

Fig. 87

Fig. 85

35

ENGINEERING

475 SIC PETROL ENGINE

CONNECTING ROD (DIMENSIONS) :Connecting rod small end

Stage parent bore bush outsidediameter mm diameter mm

Normal 23.021/23.000 23.086/23.111

Normal I 23.221/23.200 23.286/23.311

Maximum permissible taper and ovality of connecting rod 0.004 mm

small end parent bore and cylindricity 0.008 mm

Connecting rod small end bush inside diameter 20.0+0.020/0.007 mm

finished after installation) (Piston pin oiled has

thumb push fit in small end bush).

Maximum permissible out of parallelism (bend) between 0.050 mm

connecting rod small end and big end parent bores.

Centre to centre distance between connecting rod small 141.65+-0.3 mm

end and big end parent bores.

Maximum permissible twist of connecting rod 0.050 mm

Connecting rod big end parent bore diameter 48.655 /48.671 mm

Maximum permissible taper and ovality of connecting rod 0.005 mm

big end parent bore and cylindricity 0.01 mm

Bearing shells to be selected such that clearance is maintained as 0.024 to 0.075 mm

Pre-tension of connecting rod big end bearing shells 0.013-0.051 mm

Maximum permissible difference in weight of 5 gms

connecting rods in one engine

Connecting rod big end axial play 0.05 - 0.35 mm

36

ENGINEERING

475 SIC PETROL ENGINE

If necessary machine connecting rod small end parentbore to next over size.

NOTE :

Ensure that Connecting rod big end & small end axesare parallel to each other within specified limits. Ensurethat centre distance between small end & big end ismaintained within specified limit.

Oil parent bore in connecting rod.

Install new bush in such a way that slit is positionedapproximately in vertical axis.

Drill oil hole in new bush

Finish connecting rod small end bush bore on aconnecting rod boring machine. Alternatelyconnecting rod small end bush may be reamed.

Install connecting rod bearing caps without bearingshells on connecting rod.

Tighten connecting rod bearing cap mounting nutsto specified torque. Fig. 89

NOTE :

Ensure that identification numbers for connecting rod& connecting rod bearing cap are matched & notchesfor bearing shells are on same side.

Check twist and bend of connecting rod by using newpiston pin in connecting rod small end bush.

Measure twist and bend of connecting rod with feelergauge with respect to vertical face of connecting rodalignment gauge in vertical and horizontal plane at adistance of 50 mm from line joining centres ofconnecting rod small end and big end bosses.

Fig. 90 & 91

If necessary, straighten connecting rod in coldcondition. Since a slight clearance exists betweenconnecting rod bolts and corresponding connectingrod bearing cap holes, it is possible that connectingrod bearing cap once removed may be installed offcenter, by which dimension of connecting rod big endparent bore will be different in different directions.

If difference is noticed in connecting rod big endparent bore dimension, connecting rod bearing capcan be centralised by lightly tapping it with mallet inrequired direction after slightly loosening connectingrod bearing cap mounting nuts.

Fig. 91

Fig. 89

Fig. 90

37

ENGINEERING

475 SIC PETROL ENGINE

Check connecting rod big end parent bore dimension.Fig. 92

If connecting rod big end parent bore is slightly morethan maximum permissible limits, it is possible toreclaim connecting rod provided the wear is confinedonly to connecting rod bearing cap.

Connecting rod bearing cap mating surface may beslightly faced. Parent bore should then be finished ona connecting rod boring machine.

ENSURE THAT CONNECTING ROD BIG END AND SMALLEND AXIS ARE PARALLEL TO EACH OTHER WITHINSPECIFIED LIMITS. CENTRE TO CENTRE DISTANCEBETWEEN CONNECTING ROD SMALL END AND BIG ENDIS MAINTAINED WITHIN SPECIFIED LIMITS.

If one or more connecting rods are to be replaced,ensure that difference in weight of connecting rod inone engine is within permissible limits.

Install new pair of connecting rod bearing shellaccording to size of crank pin journal diameter, makingsure that securing lugs of bearing shells are properlyseated in grooves of connecting rod and its bearingcap.

Install connecting rod bearing cap with bearing shellon connecting rod.

Tighten connecting rod bearing cap mtg. nuts tospecified torque Fig. 93

Measure connecting rod bearing bore Fig. 94

IF CONNECTING ROD BIG END PARENT BOREDIMENSION IS MAINTAINED WITHIN SPECIFIED LIMITS,PROPER BEARING BORE DIMENSION IS AUTOMATICALLYACHIEVED.

However, it must be physically measured andconfirmed Measure pre-tension of connecting rodbearing shell with a feeler gauge after looseningconnecting rod bearing cap mounting nut on oppositeside of bearing shell lug -

CONNECTING ROD BEARING SHELLS ARE PRECISIONFINISHED AND SHOULD NOT BE BORED OR SCRAPED.

Fig. 92

Fig.93

Fig. 94

38

ENGINEERING

475 SIC PETROL ENGINE

Crank shaft (dimensions)

Stage Crank case main bearing bore Crank shaft main bearing journaldiameter with bearing shell mm diameter mm

Normal 50.026 / 50.065 50.0/49.98

Normal 1 49.926/ 49.965 49.900/ 49.880

Repair 1 49.786 / 49.815 49.760/ 49.730

Repair 2 49.526 / 49.565 49.500/ 49.480

Stage Connecting rod big end bore Crank pin journal diameter mmdiameter with bearing shell mm

Normal 45.007 / 45.043 44.995/44.980

Normal 1 44.907 / 44.943 44.895/ 44.880

Repair 1 44.757 / 44.793 44.745 / 44.730

Repair 2 44.507 / 44.543 44.495 / 44.480

Stage Width of 4th main bearing Thickness of 4th mainjournal mm bearing thrust washers, mm

Normal 24.052 / 24.0 2.62(2.60-2.65)

Standard 1 24.152 / 24.100 2.57(2.55-2.60)

Repair 1 24.252 / 24.200 2.52(2.50-2.55)

End play of crank shaft 0.06 - 0.226 mm

Fillet radius of main bearing journals 2.5-0.5 mm

Fillet radius of crank pin journals 2.5-0.5 mm

Width 1st, 2nd, 3rd and 5gh 24.0+0.2 mmmain bearing journals

Width crank pin journals 24.0+0.2 mm

Maximum permissible cylindricity 0.0025 mm

Ovality of main brg. journal 0.005 mm

Max. permissible ovality of crank pin 0.005 mm

Maximum permissible run out of 0.02 mm2nd, 3rd and 4th main bearing journalswhen supported at 1st and 5th mainbearing journals

Maximum permissible out of parallelism 0.010 mmbetween crank pin and mainbearing journal axis

Pre-tension of main bearing shells 0.018-0.040 mm

Hardness of crank shaft main 50-60 HRCbearing and crank pin journals

Main bearing parent bore dia in 53.8 +0.019 mmcrank case + 0.00 mm

Maximum permissible taper of 0.005 mmmain bearing parent bore

Maximum permissible ovality of 0.005 mmmain bearing parent bore.

Crank shaft journal to main 0.026 / 0.085 mmbearing clearence

39

ENGINEERING

475 SIC PETROL ENGINE

CRANK SHAFT :Clean and carry out visual inspection of crank shaft forfollowing.

l Over heating of journals, which is indicated bybluish brown colour.

l Scoring marks on journals.

l Cranks, which should be checked on magneticcrack detector.

Check crank shaft run out by supporting it on V-blockat 1st and 5th main bearing journals. Fig. 95

If run out exceeds permissible limits, straighten crankshaft in cold condition on press carefully.

Similarly check lateral and radial run outs of flywheelmounting flange.

Check crank shaft main bearing and crank pin journaldimension.

If necessary, grind crank shaft main bearing and crankpin journals to next under size.

MAINTAIN CORRECT FILLET RADII FOR JOURNALS

Care must be taken during grinding to ensure thatwidth of journals is not increased.

Should it be necessary to grind sides of 4th mainbearing journal, grind it to next over size.

Re-chamfer oil holes on journals to avoid scoring ofnew bearing shells.

Finish journals by lapping them with 320 grit lappingcloth of suitable width.

After grinding recheck main bearing and crank pinjournal dimensions.

Also recheck run out of crank shaft.

Thoroughly clean crank shaft with kerosene. Use wirebrush for cleaning oil holes.

IT IS ESSENTIAL TO RECHECK CRANK SHAFT FOR CRACKSAND BALANCE AFTER GRINDING

Apply grease to all machined surfaces, if crank shaft isto be stored. Crank shaft must always be stored invertical position.

CYLINDER BLOCK(See page a 33 & 42 for cyl. bore & block dimensions)

Check cylinder block for cracks by pressure testingmethod.

Check crank case mating surface with cylinder headfor unevenness with help of straight edge and feelergauge. Fig. 96 & 97

Fig. 95

Fig. 96

Fig. 97

40

ENGINEERING

475 SIC PETROL ENGINE

If necessary grind this surface just to clear unevenness.

Ensure that the minimum height of crank case is notless than the specified minimum height.

Thoroughly clean main bearing caps andcorresponding machined surfaces of crank case.

Install main bearing caps without bearing shells in theirrespective positions of crank case.

ENSURE THAT SERIAL NUMBERS ON CRANK CASE ANDMAIN BEARING CAPS ARE MATCHING. ALSO CAPS AREIN SERIAL ORDER AND NOTCHES FOR BEARING SHELLSARE ON SAME SIDE.

Tighten main bearing cap mounting bolts to specifiedtorque. Fig. 98

Check crank case main bearing parent boredimensions. Fig. 99 Install new pairs of main bearingshells according to size of crank shaft main bearingjournal diameter, making sure that securing lugs ofbearing shells are properly seated in grooves of crankcase and main bearing caps.

Install main bearing caps with bearing shells in theirrespective position on crank case.

Tighten main bearing cap mounting bolts in specifiedsequence to specified torque. Fig. 100

Measure main bearing bore.

IF MAIN BEARING PARENT BORE DIMENSION ISMAINTAINED WITHIN SPECIFIED LIMITS, PROPER MAINBEARING BORE DIMENSION IS AUTOMATICALLYACHIEVED.

However, it must be physically measured andconfirmed.

Fig. 98

Fig. 99

Fig. 100

41

ENGINEERING

475 SIC PETROL ENGINE

Measure pre tension of main bearing shell with a feelergauge after loosening main bearing cap mounting bolton opposite side of bearing shell lug (This is to be doneon a flat surface plate as it can not be measured onengine cylinder block because the main bearing capsare guided). Fig. 101

MAIN BEARING SHELLS ARE PRECISION FINISHED ANDSHOULD NOT BE BORED OR SCRAPED.

Select new pair of thrust washer according to crankshaft 4th main journal width.

Cylinder bores

Clean cylinder bores thoroughly

Check cylinder bore dimension, taper and ovality.Fig. 102 & 103

If taper and ovality is found to exceed specified limitor bore is excessively worn out machine cylinder boreto next over size.

Record the readings in Engine inspection sheet no. 2given in this manual.

Cylinder bore remachining and honing procedure:

In order to obtain optimum performance of engine,the machining procedure to be adopted is givenbelow:

Selection of size to which bore should be machinedshould be done as follows :

a.a Bore diameter of worn out cylinder bore.

b. Size of next repair size piston available.

c . Recommended clearance between piston andbore.

d. Required bore diameter for remachining = b + c

Boring depth form cylinder head mountingface : 135mm.

Machine all bores (size b + c) leaving 0.050 to0.070 mm stock for honing.

IT IS VERY IMPORTANT THAT AXIS OF CYLINDERBORES ARE PARALLEL TO EACH OTHER AND ARE ATRIGHT ANGLE TO AXIS OF CRANK SHAFT. THEREFOREWE RECOMMEND USE OF PILLAR TYPE BORING ANDHONING MACHINE.

Therefore, we recommend use of pillar type boringand honing machines.

Clean cylinder bores, bearing surfaces and oil passagesin crank case thoroughly.

Fig. 101

Fig. 102

Fig. 103

Schematic Sketch : Main bearing shell pretension checking

Þ

Þ

PRETENSIONGAP

SURFACE PLATE

BOLT LOOSENEDBOLT TIGHTENED

42

ENGINEERING

475 SIC PETROL ENGINE

LUBRICATION SYSTEM :

OIL PUMP

Unscrew screws holding oil pump to cyl. block andremove the oil pump Assembly Check oil pump forflow rate at specified rpm. Check for any leakage atsealing plugs.

Check functioning of Pressure relief valve. If theperformance of the pump is not satisfactory, thenreplace the oil pump assembly.

Fit oil pump Assembly with new gasket.

Flow rate measured against back pressure of 3kg/cmsq.should be as follows using SAE-30 oil.

Pump rpm Minimum flow rate in Ipm

4000 28

2000 14

800 5.6

Engine oil pressure with coolant temperature of 70deg. C at idling speed

800+50 rpm - 1 bar

at 5000 rpm - 3 bar

Oil Pressure Switch

NC contact opening pressure :0.9 /0.6 bar

Check water jackets and oil passages for leakages/cracks at air pressure of 5 bar under water. The blockwith any such defects should be discarded.

HONING :

We give below the stone grit sizes and machine speedsto be used during different stages of honingoperations.

Sr. Operation Stone Machine Remove StrokeNo. grit rpm material speed

Size (mm) mtr/min

1 Roughing 181 250 0.035 27/26(Stage1)

2 Roughing 181 250 0.020 25/24(Stage2)

3 Finishing 80 180 0.010 19( Base honing)

4 Finishing 400 180 0.005 19.8(Plateau honing)

Recheck block for cracks etc. by pressure testing asper procedure.

Apply grease to machined surfaces, especially ifengine assembly is not to be taken up immediately..

Cylinder Block (Dimensions) - in mm

Height of crank case 265.8/265.6

(Dimension A&B) Fig. 104

Maximum permissible unevennessof crank case mating surface with cylinder

head 150x150 : cross wise ‘D’ Fig. 104 0.015

: length wise ‘C’ Fig. 104 0.030

Maximum permissible out off 0.2parallelism between crank case top andbottom machined surface

Maximum permissible shift in 0.25 mmperpendicularity of cylinder borefrom crank shaft axis whenchecked at from crank shaft centre line

Maximum permissible taper and 0.007ovality of cylinder bore

A

B

C

D

Fig. 104

43

ENGINEERING

475 SIC PETROL ENGINE

COOLING SYSTEM :

WATER PUMP

Check water pump for free rotation. Check waterpump for flow rate at specified rpm. Check for waterleakage through leakage hole. It indicates that the sealis damaged and leaking. Replace the water pump ifnecessary.

Water pump characteristics :

ENGINE RPM PUMP RPM FLOW RATE AT BACK PRESSURE=0.3 BAR

(LITRES PER MINUTE)

2000 2100 40

3000 3150 60

4000 4200 80

5000 5250 100

5500 5775 110

Thermostat

l Start opening temperature - 78 0C ± 2

l Full open temperature - 90 0C ± 2

l By pass port closed at or before

l Leakage through main valve (including seepagehole) at room temperature and pressure of1 kg/cm2 : 150-250 ltrs/hr

l Maximum leakage through by pass at full opentemperature or main flow rate of130 + 5 lpm : 1.5 lpm

Thermostat is installed in cooling system between cyl.head & radiator inlet tank.

The working principle of thermostat :

1. For cool engine (immediately after starting) :Thermostat does not allow water to flow toradiator (Thermostat valve in closed position)instead water flows through thermostat by-passoutlet to engine. Thus short circuiting of radiatorwhich helps for attaining engine workingtemperature in very short period. Fig. 105

2. As soon as the cooling water temperaturereaches opening temperature of thermostat, thethermostat valve starts opening gradually andwater flow starts to radiator. At the same timethermostat by pass starts closing gradually.

Fig. 105

Fig. 106

3. As the engine cooling temperature reachesthermostat full open temperature, thermostatvalve opens fully and thermostat by-pass valvecloses completely. Under such conditionmaximum quantity of engine cooling water flowsto radiator. Fig. 106

THEMOSTATE CLOSED

THEMOSTATE OPEN

44

ENGINEERING

475 SIC PETROL ENGINE

Satisfactory operation of thermostat is very muchessential for :

l Efficient engine operation

l Longer engine life.

Defective thermostat may cause

l Over cooling due to thermostat valve sticking infull open position

l Over heating due to thermostat valve sticking inpartial/full closed condition

When above defects are observed, thermostat needschecking.

Checking of thermostat element

1. Remove thermostat element from thermostathousing Fig. 107

2. Mount thermostat element in suitable fixture andplace the fixture in a vessel filled with water.

3. Fix dial gauge with its spindle on valve surfacewith a pretension @ 0.5 mm

4. Heat the vessel and measure the watertemperature with proper thermometer

5. Note down the temperature when dial gaugeneedle starts moving indicating valve opening.

6. Note down the water temperature for needlemovement of 8mm (valve fully open position)

7. The opening temperature (Sl.No.5) and fully opentemperature (Sl.No.6) as measured should be asmentioned in table.

If they do not meet the specifications, replace thethermostat element.

Cylinder block Assembly :

Install main bearing shells, in the block.

Install thrust washers in crank case at their respectivelocation on 4th main bearing sides.

Apply light coat of engine oil to main bearing shellsand main journals.

Install crank shaft Fig. 108

Install 4th main bearing cap with thrust washers.

Install 1st, 2nd, 3rd and 5th main bearing caps withshells in their respective position on crank case.

Tighten main bearing cap mounting bolts evenly anduniformly to specified torque (first 3rd cap, next 4thand 2nd, lastly 5th and 1st) Fig. 109

Fig. 107

Fig. 108

Fig. 109

45

ENGINEERING

475 SIC PETROL ENGINE

Check that end float of crank shaft is within specifiedlimits. Fig. 110

Install rear oil seal using drift 2702 5890 0608 in crankcase rear cover. Fig. 111

Clean mating surfaces of crank case & rear cover.

Fit crank case rear cover with new gasket Fig. 112

Locate fly wheel on crank shaft rear flange.

Screw-in fly wheel mounting screws.

Insert flywheel locking pin

Tighten fly wheel mounting screws to specifiedtorque.

Remove flywheel locking pin.

Remove connecting rod bearing cap with shell.

Assemble connecting rod in piston such that when youhold the piston in your hand, the arrow mark on thepiston crown is towards left and the cooling jet onconnecting rod is towards you.

Insert piston pin. Fit piston pin spring clip. Fig. 113

Apply oil on piston, piston rings, cylinder bore andbearing shells.

Turn crank shaft and bring crank pin journal to topmost position into which connecting rod with pistonis to be fitted.

Insert connecting rod with piston upto piston ringsinto cylinder bore with arrow on piston crown pointingtowards front.

Fig. 111

Fig. 112

Fig. 110 Fig. 113

46

ENGINEERING

475 SIC PETROL ENGINE

Stagger piston ring gaps such that they are 120 deg.apart. Clamp piston ring compressor over piston ringssuch that piston with piston rings can slide inside it.Fig. 114

Push piston gradually inside cylinder bore usingwooden handle of mallet till connecting rod locateson crank pin journal. Slowly rotate crank shaft,simultaneously pushing piston till crank pin journalreaches BDC position.

Install connecting rod bearing cap with bearing shellon connecting rod ensuring that bearing shell lugs areon same side. Fig. 115

Tighten connecting rod bearing cap mounting nutsto specified torque. Fig. 116

Assemble other connecting rods with piston in samemanner.

Check end play of connecting rods Fig. 117

Fix oil pump gasket

Install oil pump Assembly with gasket.

Fig. 115

Fig. 116

Fig. 117Fig. 114

VALVE POCKETS

LUGS

JET

47

ENGINEERING

475 SIC PETROL ENGINE

Tighten the oil pump mtg. screws to specified torque.Fig. 118

Fit oil pump strainer with gasket. Fig. 119

Fit water pump with new gasket. Fig. 120

Install - Oil sump Fig. 121

- Timing gear rear covers

- Timing belt tensioner

- Crankshaft gear

Install crank shaft pulley Assembly (An additional multigroove pulley provided for deluxe version, for ACcompressor drive) in position.

Lock fly wheel with timing pin Fig. 122Fig. 120

Fig. 121

Fig. 122Fig. 119

Fig. 118

48

ENGINEERING

475 SIC PETROL ENGINE

Screw in crankshaft pulley mounting bolt with spacerand tighten it to specified torque. Fig. 123

Fit

l Alternator top mounting bracket

l Alternator bottom mounting bracket

l Alternator

l NEW oil filter

l Fit water inlet elbow with gasket.

Fit clutch disc using mandrel (2702 5890 0250)(Fig.124) and clutch pressure plate (Fig. 125), for anyof cylinder head on block, timing bolt fitment etc.

FOR ASSEMBLY OF CYLINDER HEAD ON BLOCK, TIMINGBELT FIT MENT ETC. PLEASE REFER RESPECTIVESECTIONS OF THIS MANUAL.

AIR CLEANER Fig. 126

For regular cleaning as per maintenance schedule :

l Unclip and remove housing cover, and removeelement. Fig. 126

l Clean it gently by tapping on clean table.

l Use compressed air, at a very low pressure, forcleaning the element

l Check the condition of rubber sealing

l Check element for major rupture or puncture ofproper pleats

Fig. 124

Fig. 125

Fig. 126Fig. 123

AIR FILTER

49

ENGINEERING

475 SIC PETROL ENGINE

l Replace element if any rupture or puncture isobserved.

l Always use GENUINE air filter element to ensurelong engine life.

l Install paper filter element

l Fit housing cover and clamp it firmly with theclips

l Check condition of air hose

l Check condition of rubber cuff on air filter andreplace it if necessary.

ENGINE TESTING

After assembly of the engine, mount engine on testbed, prepare engine for starting and testing in thefollowing manner.

Connect oil pressure gauge and temperature gauge.

Connect water hose to and from radiator. Fill coolant(water and anti-corrosive agent) in the cooling system.Fit radiator cap.

Fill required quantity of recommended running-in oilin the oil sump.

Mount air cleaner assembly on test bed suitably.Connect air cleaner outlet to engine intake usingsuitable hoses.

Make suitable linkage for controlling accelerator lever.

Connect exhaust pipe to exhaust manifold.

Connect battery cables to starter motor. Ensure that -ve terminal is earthed.

Crank engine with accelerator lever in idling position.Allow oil to be circulated through the system. Checkand ensure that oil pressure indicated by gauge issatisfactory.

Slightly raise the engine speed and check for any oil,fuel, water and air leakages. Rectify if any. Check colourof the exhaust gas. Check for any unusual noise fromthe engine.

Connect engine to dynamometer and run for runningin test as per schedule.

Engine running in test schedule :

Engine Speed Time (minutes) Torque (mkg) (rpm)

800 5 0.0

2000 5 2.3

2500 5 4.6

3000 5 5.8

3500 5 4.9

2500 5 8.2

After running in test of the engine, reducedynamometer load to zero and allow engine to run atidling speed for about 5 minutes and then stop it.

Allow engine to cool down for about 3 hours. Thenremove cylinder head cover.

Loosen cylinder head mounting bolt by quarter turnand retighten immediately to 7 mkg torque in thecorrect sequence.

Complete cylinder head tightening operation in thesame sequence and with the same torque.

Start the engine and check for any fuel leakages.Rectify, if necessary.

50

ENGINEERING

475 SIC PETROL ENGINE

CARBURETTOR : Fig. 127

GENERAL DESCRIPTION

Carburettor is a twin barrel down draught, progressivecarburettor of modern design. It uses die castAluminium mixing body. Throttle body and floatchamber cover in order to reduce weight and toprevent deformation. The basic functions and variousfeatures of the carburettor are as follows :

1. LEVEL SYSTEM :

The spring loaded needle valve and float help inmaintaining constant fuel level even during vibration.A filter on the upstream side of the needle valve orificeprevents dust entry in the circuits of the carburettor.

2. FUEL RETURN CIRCUIT : Fig. 128

A fuel return circuit is provided in this carburettor inorder to avoid vapour lock problem. This ensures thatthe fuel pump delivers more fuel than the enginerequirement, the extra fuel returning to the tank andgetting cooled by the bulk of the fuel in the tank.

Thus the fuel pump operates relatively cooler therebyavoiding vapour lock problem.

The returning fuel circuit is so arranged in thiscarburettor that it surrounds the accelerating pumpchamber thereby preventing vapour formation insideaccelerating pump also.

3. PRIMARY AND SECONDARY BARRELS :

The twin barrel carburettor design is adopted in orderto ensure satisfactory low end flexibility at the sametime achieving maximum top end power.

During low speed road driving conditions when theair quantities inhaled by the engine are small, only theprimary barrel works thereby ensuring high venturivelocity for proper atomisation of the fuel.

Beyond certain predetermined operating conditionswhen the air quantity increases, this signal is used toopen the secondary barrel by the PNEUMATICCOMPOUNDING DEVICE. At high speed full loadconditions, both the barrels are open therebyproviding adequate passage for air flow.

4. PRIMARY CIRCUIT :

4.1 SLOW SPEED CIRCUIT : Fig. 129

The mixture requirement for the engine to idle isprovided by this circuit. This circuit is incorporated inthe primary barrel of the carburettor.

Fig. 128 FUEL RETURN CIRCUIT

Fig. 129 SLOW SPEED CIRCUIT

Fig. 127

PRIMARY MAIN JET

SLOWAIR HOLE NO. 1

PRIMARYSLOW JET

BYPASSPORT

IDLE PORT

PRIMARY MAIN JET

51

ENGINEERING

475 SIC PETROL ENGINE

When the engine starts to run, the fuel in the floatchamber flows out through the main jet and reachesthe pilot (slow) jet. There, the incoming fuel is meteredand mixed with the air metered at pilot (slow) air holes.

This air-fuel mixture is sprayed out from idle port.During idling, this mixture gets mixed with the airflowing into the main bore past the throttle, providingthe correct mixture for idling.

The air-fuel mixture can be made leaner or richer bytightening or loosening the idle mixture adjustingscrew - Pilot screw. This screw can be made tamperproof by fitting a plastic cap over it.

As the throttle is opened slowly, the depression is feltat the bypass ports and mixture is sprayed throughthese ports also.

This region of operation is called progression and thistakes care of the mixture requirement of the enginebefore the main circuit becomes operational.

4.2. MAIN CIRCUIT : Fig. 130

When the throttle is opened wider, a strongerdepression is created at the primary inner venturi.

The fuel in the float chamber is metered at primarymain jet and flows into primary bleed pipe. There, itgets mixed with the air metered at primary main airholes.

This emulsified air-fuel mixture is sprayed into theinner venturi through the primary main nozzle.

5. SECONDARY CIRCUIT : Fig. 131

When the primary throttle valve opens wider than apredetermined value, the secondary circuit is broughtinto operation.

The vacuum developed at the primary venturi istransmitted through a hole and communicated to thedepression chamber of the pneumatic compoundingdevice.

When the vacuum exceeds the spring force in thedepression chamber, the diaphragm is pulled up asshown in the figure. This movement of the diaphragmcauses the secondary throttle to open as it is linked tothe diaphragm, thereby creating a depression at thesecondary bypass port.

The fuel from the float chamber gets metered throughthe secondary main jet and reaches secondary pilotjet. There it is metered and mixed with the air whichis metered at the secondary pilot air hole. The air-fuelmixture is sprayed out of bypass Port. When the

Fig. 130 MAIN CIRCUIT CUM ENRICHMENT CIRCUIT

Fig. 131 SECONDARY CIRCUIT

primary throttle is opened further, the vacuum signalin depression chamber increases further causing thesecondary throttle to openwider thereby creating astronger depression at the secondary inner venturi.The fuel metered at the secondary main jet flows intosecondary bleed pipe. There, it gets mixed with theair which is metered at secondary main air holes. Thisemulsified air-fuel mixture is sprayed out through thesecondary venturi.

6. ENRICHMENT CIRCUIT : Fig. 130

When the engine is accelerated and comes under highload, the negative pressure in intake manifold goesdown (The negative pressure of intake manifold is highwhen the throttle valve is closed and, as the throttlevalve opens it goes down).

1

2

3

4

5

6

7

8

1. PRIMARY MAIN JET

2. PRIMARY BLEED PIPE

3. MAIN HOLE NO. 2

4. MAIN HOLE NO. 1

5. INNER VENTURI

6. SPRING

7. ENRICHMENT VALVE

8. ENRICHMENT JET

4

1. PRIMARY THROTTLE VALVE2. PRIMARY SIDE3. SECONDARY SIDE4. DEPRESSION CHEMBER5. DIAPHRAM6. SECONDARY THROTTLE VALVE

32

1 14 6 5

6

1211

10

98

73

7. SECONDARY MAIN HOLE8. BLEED PIPE9. SECONDARY PILOT AIR HOLE10. SECONDARY PILOT JET11. SECONDARY MAIN JET12. BYPASS PORT

52

ENGINEERING

475 SIC PETROL ENGINE

The enrichment valve is attached to the diaphragm,one side of which is in communication with manifoldvacuum while the valve is spring loaded. When themanifold vacuum is high, the diaphragm is pulled toone side thereby keeping the valve closed.

When the vacuum goes down, the enrichment valveis push opened by spring force and the fuel is meteredby the enrichment jet and then flows into bleed pipeof the primary main circuit.

This additional fuel makes the mixture richer underhigh load conditions, without affecting part load fueleconomy.

7. ACCELERATING PUMP SYSTEM : Fig. 132

This system helps the carburettor to respond withoutdelay when the accelerator pedal is depressedsuddenly while the engine is running in its low speedrange or is idling.

The actuating lever of the pump is connected to theprimary throttle shaft so that when the primarythrottle opens suddenly, the pump lever pushes theaccelerating pump membrane forward, therebyclosing the suction ball valve and lifting the dischargeball along with the weight.

The fuel gets discharged through the pump nozzleinto the primary bore. This supplies an instantaneouslyrich mixture to take care of the transient acceleratingconditions.

When the accelerator pedal is released, the membraneis set back to the original position by the action of thepump spring. In this state, the fuel in the float chamberopens the suction ball valve and enters the pumpchamber.

8. ANTI-DIESELING SYSTEM : Fig. 133

This system is used to prevent “dieseling” (also knownas engine run-on, that is the engine does not stop evenwith the ignition turned off ). With the ignition keyturned on, current flows in the solenoid coil of thesolenoid valve generating a magnetic force. This pullsthe plunger in the valve and opens the passage orslow mixture.

When the ignition key is turned off, the magnetic forcedisappears and the plunger is brought to the originalposition by the action of the spring in the solenoidvalve thus the slow mixture passage is cut off andhence the engine stops.

9. EMISSION CONTROL SYSTEM :

When the car is travelling at high speed and the

Fig. 133 ANIT-DIESELING SYSTEMS

Fig. 132 ACCELERATING PUMP

accelerator pedal is released, the wheels will bemotoring the engine at a higher speed.

Consequently, the vacuum in the inlet manifold andthe combustion chamber increases too much causingincomplete combustion resulting in an increase inunburnt HC.

A “ Delay Valve” explained in para 14, delays the throttleclosure thus preventing manifold vacuum frommissing too much thereby reducing the unburnt HC.

10. COLD STARTING SYSTEM :

A manually operated choke is provided to assist in coldstarting. This system is operated by pulling the chokeknob provided on the dashboard.

SLOLENOID VALVE

SLOW MIXTURE

PASSAGE

PRIMARYTHROTTLEVALVE

SUCTION BALLVALVE

ACCELERATINGPUMP LEVER

ACCELERATINGPUMPCHAMBER

ACCELERATINGPUMPMEMBERENCE

DISCHARGEBALL VALVE

VALVEWEIGHT

PRIMARYSIDE

PUMPNOZZLE

53

ENGINEERING

475 SIC PETROL ENGINE

When the knob is pulled out fully, the choke valvemounted on the primary barrel air intake closes theair passage, at same time opening the primary throttleslightly through a system of levers.

When the engine is cranked a depression is felt at theprimary main system which discharges a very rich airfuel mixture into the inlet manifold.

As soon as the engine fires, the increased air flowcauses the strangler valve to open because it iseccentrically mounted. This makes the mixture leanto the required extent as otherwise the engine willstall due to too rich condition.

11. AIR INDUCTION SYSTEM : REFER Fig. 134

This system is incorporated to provide the inductionair required for Rapid combustion to improvecombustion efficiency.

During idling, when the primary throttle valve is nearlyclosed, air is taken into induction system through theholes on the upstream side of the throttle.

This air, whose flow is dependent on the pressuredifference between the cylinder and the upstreamside of the throttle, flows through the nozzle creatinga swirl inside the combustion chamber.

As the throttle valve is open, fuel mixture flow isinduced through these holes due to the pressuredifference between the cylinder and throttle valvearea. As the mixture flow increases the strength of theswirl also increases.

At WOT the pressure difference between the cylinderand the throttle decreases and hence the flow throughthe induction system also decreases.

This system therefore helps to promote lean mixtureburning due to creation of swirl and is effectively usedunder light load conditions.

This carburettor has provision for holes controlled byprimary throttle and as well as passages leading tothe air induction passage in the induction manifold.

12. A.C. IDLE - UP SYSTEM : (If A.C. fitted)

When the Air conditioner switch is ON, the compressorload tends to reduce the engine speed leading toengine instability/stalling. To overcome this, AC IDLE-UP system is installed on the carburettor.

When the electro magnetic clutch of the AC

Fig. 134

compressor gets energised, a solenoid valve, whichis connected in series is actuated.

When the solenoid opens, the manifold vacuum isapplied to the capsule, thereby pulling the diaphragmin the capsule. This causes the throttle to open,thereby increasing the engine speed.

The speed at which the engine runs with Airconditioning compressor ON can be adjusted by ascrew which is provided in the carburettor.

The capsule is generally supplied by theAIRCONDITIONER manufacturer.

The Dashpot unit has the A/C IDLE-UP systemincorporated in its design.

PRIMARY MAIN JET

SLOWAIR HOLE NO. 1

PRIMARYSLOW JET

BYPASSPORT

IDLE PORT

PRIMARY MAIN JET

54

ENGINEERING

475 SIC PETROL ENGINE

13. RESTART SYSTEM : REFER Fig. 135 & 136

Appropriate opening of the throttle valve at the timeof restarting the engine does away with the need forstepping-on of accelerator pedal. The operation is asfollows :

(a) While engine is stopped, the restart adjusting screwgets pushed by a spring in the restart actuator andthe throttle valve is opened appropriately.

Thus during Hot-restarting of engine, the throttle valvestays open and this overcomes the difficulty inrestarting due to excessive concentration of fuel inthe inlet system of the engine. Fuel accumulation isdue to vapours of evaporated fuel finding their waythrough internal vent.

(b) After starting the engine, the negative pressure ofthe intake manifold is transmitted to the restartactuator after certain time delay by VACUUMTRANSMITTING VALVE.

Then the diaphragm in the actuator pulls up the rodand the throttle valve opens to the normal idling levelby the effect of return spring of the throttle valve.

14. DELAY VALVE Fig. 137

The function of the valve is to delay the throttle closureduring deceleration.

The valve consists of two pipes (Black and Brown),which are connected by hoses to the throttle body(Black) and the throttle positioner (Brown).

The valve also consists of a non-return valve, whichallows air only from throttle body (Black) side to thethrottle positioner (Brown) side.

When the throttle is opened, the vacuum in the blackside is less than the vacuum in the brown side.Therefore air enters through the one-way valve to thebrown side from the black side because of thepressure difference.

When the throttle is closed, the vacuum in the blackside is higher than the vacuum in the brown side.Therefore air tries to enter into the black side fromthe brown side. Since the valve is one way, air has toenter through the orifice and hence the delay inthrottle closure.

Fig. 136

Fig. 137

Fig. 135

CARBURATOR

RESTARTACTUATOR

INTAKEMANIFOLD

GASFILTER BLACK BROWN

UTV

TO INTAKE MANIFOLD

BLACK PIPE BROWN PIPE

FILTERNON RETURN VALVE

CRIFICE

55

ENGINEERING

475 SIC PETROL ENGINE

CARBURETTOR RELATED FAULTS-DIAGNOSIS &CURE

1. Exploded view of the carburettor along with listof parts is enclosed for understanding thecarburettor Fig.138.

2. Proper sequence of the assembly is to befollowed carefully while dismantling any part inthe carburettor.

Particular care is required while dismantlingPower(enrichment) Valve Assembly CoastingRicher Assembly Primary pilot jet and primary &secondary main jets.

3. When reassembling the parts tighten thefasteners to specified torques.

Sr. No. Description of part Torque (cm.kg.)

1 Primary Main Jet 18.0

2 Secondary Main Jet 18.0

3 Secondary Pilot Jet 17.5

4 Enrichment Jet 7.0

5 Inlet Nipple 70.0

6 Return Line Nipple 40.0

7 FID Bolt (M8X1) 60.0

8 Primary Throttle End Nu 60.0

9 Sec. Depression Chamber Nut 60.0

10 M4X0.7 Screw 20.0

11 M5X0.8 Screw 35.0

12 M6X1 Screw 50.0

4. Make sure that the orifice in the brass pipe usedfor the communication of manifold vacuum to theenrichment valve is not blocked.

5. When reassembling or replacing the Primary &Secondary Main Jets, ensure that they are notinterchanged; use the jet with same number(stamped on its head) as the one being removed.

The number (size) of the primary main jet shouldbe smaller than that of the secondary main jet.

The enrichment jets assembled in the MixingBody and Float Chamber Cover are different in

size and they should not be interchanged. Thebigger jet is to be assembled in the FloatChamber Cover.

6. Primary Pilot Jet must be assembled properlywith the lock plate in correct position so that thejet sits properly on the seat. Do not forget toassemble “O” ring in both primary & secondarypilot jets.

7. Do not remove primary & secondary innerventuries. They are press fitted.

8. “Carburettor cleaner”. Such liquids if availableshould be used otherwise petrol may be usedfor cleaning, taking the usual precautions againstfire hazards.

9. Damaged gaskets and “O” rings should bereplaced before assembly.

10. Throttle body assembly should not bedismantled. Do not disturb the SecondaryThrottle stop screw since it is factory set.

11. The throttle body assembly is assembled withtwo fixing screws. One screw is white in colourassembled with copper washer and the otherscrew is yellow in colour with regular springwasher. While assembling, do not interchangethese screws and washers.

12. Install the choke cable to the carburettor bodywith the choke knob pulled out about 7 mm toensure choke valve returns completely to theoriginal position.

13. Check to ensure that the carburettor solenoidmakes “Clicking” sound when ignition switch keyis turned “ON” and “OFF” (without starting theengine).

14. Solenoid assembly should not be dismantled.While refixing the solenoid assembly proper carehas to be taken for earthing the terminal.

15. If the float is punctured or damaged petrol willbe present inside the float which can be foundby visual observation.

In this case do not attempt to repair the floatand replace with genuine UCAL MIKUNI sparefloat.

While handling the float extra care has to betaken and the float should not be dropped onthe floor.

56

ENGINEERING

475 SIC PETROL ENGINE

Fig. 138

26

27

35

63

336125

27

68

72

69

12

212322

18

19

70

17

20

37

32

62

648

5966

65

67

5

2410

9

8011

1

229A

3

4039

28A 30A4

38

10

31

31D

31B

10

45

44

43

42

4748 74

49

50

31E31C

14

46

1516

13

57

ENGINEERING

475 SIC PETROL ENGINE

EXPLODED VIEW OF UCAL MIKUNI DIDS CARBURETTOR WITH THROTTLE

POSITIONER SYSTEM FOR TELCO CAR PART DESCRIPTION

EXP. REF. DESCRIPTION NO. OFF

1 Primary pilot jet 1 off

2. Primary pilot jet O-ring 1 off

3. Primary pilot jet lock plate 1 off

4. Fixing screw 1 off

24 Primary main jet 1 off

5. Secondary main jet 1 off

6. Secondary pilot jet 1 off

7. Secondary pilot jet O-ring 1 off

8. Float chamber cover gasket 1 off

12. Return line O-ring 1 off

25. Float chamber cover Fixing screw 6 off

26. Float chamber cover Fixing screw 1 off

27. Float chamber cover Fixing screw washer 7 off

9. Pump outlet steel ball 1 off

10. Pump weight 1 off

11 Pump body gasket 1 off

13. Accelerating pump spring 1 off

14. Acc pump membrane assy 1 off

15. Acc pump fixing screw 4 off

16. Acc pump spring washer 4 off

31. Power valve diaphragm Assembly 1 off

31D Power valve spring 1 off

19 Needle valve assy 1 off

20. Needle valve filter 1 off

21. Needle valve guide plate 1 off

22. Guide plate fixing screw 1 off

23. Guide plate screw washer 1 off

28A Solenoid Assembly 1 off

29A Solenoid O-ring 1 off

30A Solenoid fixing screw 1 off

17. Float 1 off

18. Float toggle spindle 1 off

31A Valve body assy 1 off

31B Pump body assy 1 off

31C Pump body fixing screw 2 off

31D Power valve spring 1 off

31E Pump body fix screw washer 2 off

58

ENGINEERING

475 SIC PETROL ENGINE

Fig. 139

26

27

35

63

336125

27

68

72

69

12

212322

18

19

70

17

20

37

32

62

648

5966

65

67

5

2410

9

8011

1

229A

3

4039

28A 30A4

38

10

31

31D

31B

10

45

44

43

42

4748 74

49

50

31E31C

14

46

1516

13

59

ENGINEERING

475 SIC PETROL ENGINE

74 Power valve hose 1 off

32. Depression chamber assy 1 off

35 Depression chamber fix screw 1 off

89 Depression chamber fix screw 1 off

39. Idle speed adjuster screw

40. Spring 1 off

41. Insulating gasket Assembly 1 off

42. Throttle body fix screw 1 off

43. Spring washer 1 off

44. Throttle body fix screw 1 off

45. Throttle body fix screw 1 off

45. Throttle body fix sc AI washer 1 off

46. Pilot screw washer (rubber) 1 off

47. Pilot screw washer (AI) 1 off

48. Pilot screw spring 1 off

49. Pilot screw 1 off

50. Pilot screw cap 1 off

62. A/C idle up 1 off

68. Nut 1 off

64. E-ring for A/c idle up 1 off

69. Throttle positioner 1 off

70. E-ring for throttle positioner 1 off

72. Delay valve 1 off

EXP. REF. DESCRIPTION NO. OFF

60

ENGINEERING

475 SIC PETROL ENGINE

16. Clean all the parts and jets only with petrol andcompressed air and do not insert wires or drillsinto the jets.

17. Power (enrichment) Valve assembly may beremoved for cleaning. While dismantling, notethe sequence in which each part is assembled.

While reassembling, assemble in the reverseorderof dismantling as otherwise the systemwill malfunction and cause excessive fuelconsumption. refer.

18. While dismantling and reassembling the FloatChamber Cover proper care shall be taken notto damage or miss the return pipe “O” ring.

19. A loose stainless steel ball and brass pumpweight positioned in the mixing body pumpoutlet should not be sticky or lost.

20. Pilot screw should not be fully screwed homewith excessive force to avoid damage to the tip.

REMOVAL OF CARBURETTOR FROM VEHICLES :

1. Disconnect battery negative cable from battery.

2. Remove air cleaner case

3. Disconnect carburettor solenoid valve lead wirefrom carburettor.

4. Disconnect accelerator and choke cables fromcarburettor.

5. Disconnect vacuum hose from distributorvacuum advancer.

6. Disconnect fuel inlet and return hoses fromcarburettor.

7. Check all around carburettor for any other partsrequired to be removed or disconnected forremoval of carburettor and remove ordisconnect whatever necessary.

8. Then remove carburettor from intake manifold.

CLEANING PROCEDURE :

1. Spray carburettor cleaner and compressed air inthe passages of the primary pilot jet circuit,secondary pilot jet circuit, main-Jet (primary &secondary) and solenoid circuits.

2. Spray carburettor cleaner in the accelerationpump bowl return jet and in the pump body andensure no blockage in the jet. Also spraycarburettor cleaner and compressed air in theacceleration pump nozzle in the mixing body and

ensure no blockage. Spray cleaner in theacceleration pump inlet an doutlet passages andensure free movement of the outlet ball andweight (visual).

3. Spray carburettor cleaner on the power valve andensure free movement of the valve and properseating. Replace power valve with new one ifdiaphragm rotation is observed or material isdeteriorated.

4. Clean float chamber blowl in the mixing bodywith carburettor cleaner to remove gumformation. If gum formation is observed, replacethe venturies as it is impossible to clean the insideof the venturi with any type of cleaner.

NOTE :

When removing the venturies care to be taken to usenylon mandrel to tap it out and not screw driver ornose plier.

5. If there is carbon /gum deposit only on the airbleed holes then clean by spraying carburettorcleaner and compressed air.

6. If there is carbon deposit on the throttle valvesand throttle bore & shafts clean by sprayingcarburettor cleaner, ensuring free movement ofthe secondary throttle shaft and no blockage inthe pilot by-pass passages.

7. Check gasket surface of the mixing body andthrottle body and remove all traces of gasketmaterial sticking to the surfaces.

8. Replace all jets with gum deposit with genuinejets of the same size, as any carburettor cleanerwill not be effective in removing solidified gumfrom the jet metering hole.

9. Replace needle valve micro filter in case ofexcessive deposit or damage.

61

ENGINEERING

475 SIC PETROL ENGINE

INSTALLATION OF CARBURETTOR ON CAR

Installl in reverse order of removal

ADJUSTMENT ON CAR

Procedure for setting idling speed (Idle speed andIdle mixture adjustment to be done on warmed upengine).

Without switching the air conditioner “ON” adjustidle speed and idle mixture according to thefollowing procedure.

(a) Adjust idle speed to 800 R.P.M. by turning theidle speed adjusting screw.

(b) With engine idling at 800 r.p.m., turn pilot screwclockwise or anticlockwise and set it where thehighest engine speed is obtained (This is the bestidle position.)

(c) Perform above operation on idle speed adjustingscrew and pilot screw once again, and thenadjsut idle speed to 800rpm with idle speedadjusting screw.

(d) Upon completion of the work so far, readjustengine idle speed to the specification by turningpilot screw slowly.

MAINTENANCE :

The maintenance of the carburettor is merely aquestion of cleaning it from time to time in order toavoid blockage of the jets and channels. For this, it ispreferable to use compressed air Never use wire forcleaning the jets. Also check periodically for tightnessof flange securing nuts, main and pilot jets. Make surefrom time to time that there is no side play inthe throttle spindle. Install the choke cable to thecarburettor body with the choke knob pulled outabout 7mm to ensure choke valve returns completelyto the original position. Maintaining a full tank ofpertrol, does not allow the fuel tank to rust, reducesrust deposition in the carburettor, and reducesevaporation losses. When using choke do not openthrottle as it may cause flooding. The air filters shouldbe cleaned regularly to improve the performance ofthe engine.

CHOCK VALVE :

Check to be sure that, when the choke knob is pulledall the way out, the shaft of choke valve in thecarburettor will rotate, and that, when the knob ispushed in the shaft will rotate again to originalposition.

Accelerator and choke cables : Inspect these cabel forwear and tear and check to be sure that each cableconnection is sound off, If defective replaceimmediately, install and tighten the connection goodand hard.

62

ENGINEERING

475 SIC PETROL ENGINE

CARBURETTOR RELATED FAULTS-DIAGNOSIS & CURE.

Check other associated causes also as listed out in the Manual.

Condition Possible Causes Correction

1. Flooding 1. Float valve worn or presence of Clean/replace foreign matter.

2.Float punctured & containing some fuel Replace

3.Broken or defective gasket Replace

4.Loose float chamber securing screws Re-tighten

5.Valve Seat “O” ring missing or Check & replacecut or damaged

6.Return pipe “O” ring damaged missing or cut Check & replaceor damaged

2. Poor starting 1.Carburettor out of adjustment Adjust

(Hard starting) 2.Clogged fuel filter Clean/replace

3.Clogged carburettor Primary Main Jet Disassemble & Clean

4.Malfunctioning fuel cut solenoid valve Check solenoid valve forproper operation & replaceif necessary

5.Clogged Primary Pilot jet Clean

6.Defective choke mechanism Repair/replace

3. Not enough Power 1.Clogged Carburettor Jets Disassemble & Clean

2.Malfunctioning of choke system Adjust/replace

4. Engine hesitates 1. Clogged Carburettor Jets Clean(Momentary lack ofresponse as the accelerator 2.Malfunctioning accelerator pump Check & replaceis depressed)

3.Sticky enrichment valve Clean

5. Surges (Engine power 1.Leaky Carburettor Gaskets Replacevariation under steadythrottle or cruise) 2.Clogged Primary Main Jet Clean

6. Dieseling 1.Malfunctioning fuel cut off solenoid valve in Check solenoid valve(Engine continues to run carburettor for proper operation andafter ignition switch is turned replace if necessaryof; it runs unevenly andmay make knocking noise)

63

ENGINEERING

475 SIC PETROL ENGINE

7. Erratic Idling 1. Clogge Carburettor Jets Clean(Improper engine idling) (Primary main/pilot jets)

2. Incorrect Idle adjustment Adjust

3. Improper float level Check for flooding& correct

4. Malfunctioning fuel cut off solenoid valve Replace

5. Leaky or wornout manifold gasket Replace

6. Malfunctioning choke system Adjust/replace

7. “O” ring missing/cut/damaged in solenoid or Check & correctprimary pilot jet

8. Coasting Richer diaphragm puncture Replace

9. Wrong assembly of the parts of Assemble correctlyCoasting Richer assembly

8. Abnormal detonation 1.Clogged Carburettor Jets Clean

9. Overheating 1.Clogged Carburettor Jets Clean

10. High fuel consumption 1.Improper float level Check forflooding & correct

2.Malfunctioning of Carburettor choke system Repair/replace

3.Dirty or clogged carburettor jets Clean

4.Power (enrichment) Valve draphragm Replacepuncture

11.AC Idle-up not possible 1. AC Idle-up diaphragm puncture Replace AC Idle-upto set (if Fitted) assembly

64

ENGINEERING

475 SIC PETROL ENGINE

I. ENGINE MISSING AT 1200 TO 1500 RPM/FLATSPOT DURING ACCELERATION/VEHICLE JERKSDURING ACCELERATION.

CAUSES :

1. Check by pass passages 1, 2, 3, for blockage dueto gum, carbon, foreign matter deposits.

2. Check primary main jet for size and for blockagedue to gum formation.

If main jet is blocked, damaged, wrong size,replace with genuine part of the correct size.

II. STARTING PROBLEM. (ENGINE DOES NOT IDLEBUT BEHAVES NORMALLY DURINGACCELERATION.

CAUSES :

1. Check solenoid, if plunger does not move to andfro when ignition switched on replace.

REMEDIES :

1. If plunger does not move when ignition isswitched on and off replace solenoid.

III. ENGINE MISSING AT IDLE

CAUSES :

1. Check electrical.

2. Check engine manifold vacum (500 mm of Hg)

3. Check primary pilot jet for proper seating.

4. Check primary pilot jet & primary main jet forblockage due to gum, carbon, foreign materialdeposit.

5. Check volume control screw taper portion forsmooth surface.

6. Check pilot passage and by pass-1 for blockage.

7. Check insulating gasket and fcc gasket forproper sealing and seating.

8. Check for power valve leak.

REMEDIES :

1. If jets are blocked due to gum, carbon, foreigndeposits, replace them with genuine parts ofthe same size.

2. If fcc gasket and insulating gasket aremisaligned thereby blocking the fuel passageand the air passage replace and reallign themwith genuine parts of the same size.

NOTE :

Insulating gasket for 1400cc is different in size due toprimary bore size being 26 mm.

3. Remove the power valve hose from the powervalve size and check for any fuel presence. Ifpresent change power valve diaphragmassembly, with new one.

IV. IDLE RPM NOT ADJUSTING.

CAUSES :

1. Check throttle positioner tuning for tamperingin the field.

2. Check throttle positioner dep. chamber for leak.

3. Check if half arm lever is touching the idle screw.

4. Check if primary throttle shaft is sticky andreturning to original position.

REMEDIES :

1. IF throttle positioner tuning screw with yellowpaint is tampered, start the engine. Remove thehose connecting the throttle positioner andadjust the throttle positioner tuning screw toattain a idle rpm of 1500 rpm. With the enginestill running, connect the vacum hose to thethrottle positioner and check if engine rpmreduces to idle rpm as set with the Idle adjustingscrew. If engine does not idle but continues torevolve at 1500 rpm change the throttlepositioner, as it is leaking.

V. ENGINE SWITCHES OFF WHEN A.C. ISSWITCHED ON, ENGINE MISSES WHEN A.C. ISSWITCHED ON.

CAUSES :

1. Check A.C. idle tuning screw for tamperign.

2. Check A.C. idle depression chamber for leak.

REMEDIES :

1. If paint marked A.C. idle up tuning screw is foundto be tampered, tune up to achieve A.C. idle uprpm with A.C. ON 1250-1500 r.p.m. With A.C. offidle rpm should return back to normal 800-900rpm.

2. If engine gets off or misses during A.C. operationcheck A.C. depression chamber for leak, replace,if necessary.

65

ENGINEERING

475 SIC PETROL ENGINE

VI. LOW MILEAGE ON VEHICLE

CAUSES :

1. Check for right size of primary main jet, secondarymain jet and primary pilot jet.

2. Check for tampering of inner venturi, innerventuri not concentric with bore, discharge pipeloose and damaged due to mishandling.

3. Check inner venturi clogged due to gum, carbon,foreign matter.

4. Check flooding.

5. Check power valve leak.

REMEDIES :

1. If jets sizes are wrong replace jets with correctsizes of genuine jets.

2. Inner venturi is not a serviceable item andremoval of the same is not advisable in the field.Once removed please ensure that the innerventuri is concentric with the outer bore or therewill be restriction to the airflow and thecarburettor will malfunction. If the brassdischarge tube in the venturi is rotating or thebottom pipe is loose and rotating the entireventuri assembly will have to be changed.

3. If the bleed holes are blocked with gum, carbon(or) foreign matter, clean with carburettorcleaner and compressed air. If cleaning is notsatisfactor, the punched number on the side ofthe venturi denotes the size of the bleed holes.Insert the same size of drill bit to clean the holeand blow thoroughly with compressed air.

4. If the carburettor is flooding check the needlevalve for leak and the float for puncture andchange them if necessary. Ensure that the floatlevel adjustments are correct.

5. If power valve is leaking change power valvediaphragm assy., check for spring tension andchange if necessary.

66

ENGINEERING

475 SIC PETROL ENGINE

INSPECTION PROCEDURE FOR COMPONENTS

Fig. 140

1. Primary pilot air hole No. 2

2. Fuel return passage

FLOAT CHAMBER COVER

1. Inspect needle valve/seat/micro filter for wear,gum deposit or foreign matter.

2. Check primary pilot jet air hole for gum/carbondeposit.

MIXING BODY

1. Inspect primary pilot jet for gum formation.

2. Check if the primary pilot jet seating area in themixing body is ok, not damaged due totampering/deposit of foreign matter, gum orCarbon.

3. Connect solenoid to 12V supply and check forplunger movement.

4. Inspect float chamber in the mixing body for gumformation.

5. Check primary main jet and secondary main jetfor excessive gum formation.

6. Check air bleed holes on the primary venturi andsecondary venturi for carbon/gum formationand blockage.

7. Check for gum/carbon deposit on theacceleration pump bowl return Jet, and freemovement of acceleration pump outlet steel ball& weight.

8. Inspect power valve diaphragm for rotation/material deterioration.

THROTTLE BODY

1. Check throttle body for carbon formation on thethrottle valves, throttle bore, throttle shaft.

2. Check for free movement of the secondarythrottle shaft.

Fig. 140

1. Venturi air leak passage

2. Primary pilot air hole No. 1

3. Accelerating pump nozzle

4. Primary main air hole No. 1

5. Primary main air hole No. 2

6. Primary main jet

7. Secondary main jet

8. Secondary main air hole

9. Secondary pilot air hole.

12

35

4

6

87

9

1

2

67

ENGINEERING

475 SIC PETROL ENGINE

ASSEMBLY PROCEDURE : Fig. 139

1. Assemble primary pilot jet/O-ring, secondarypilot jet/O-ring, primary main jet and secondarymain jet.

NOTE :

Please ensure the right torque is used whileassembling.

2. Assemble solenoid taking care to install O-ringsand packing of solenoid and match the solenoidwith mixing body.

3. Install acceleration pump body/power valve withnew gasket.

4. Install pump outlet steel ball and weight.

5. Assemble float chamber cover with mixing bodyafter replacing gasket with new one taking careto follow a cross pattern for tightening.

6. Assemble the throttle positioner, depressionchamber assembly on to the float chambercover.

7. Install pilot screw to the throttle body by fullyscrewing in taking care not to use excessive forcewhile tightening, and then screwing out by 2 3/8 turns.

8. Assemble throttle body to the mixing body withnew insulating gasket ensuring that the fourfixing holes perfectly match and the gasket doesnot protrude in the throttle bore and causerestriction to high speed mixture flow.

9. Connect all linkages/O-rings, namely choke rod,secondary Depression chamber, accelerationpump rod, fish lever spring and hoses.

NOTE :

1. While assembling insulating gasket ensure thatthe gasket face on the mixing body and throttlebody is clean and free of any bits of old gasketsticking to the surface which would causeimproper seating and vacuum leakage.

2. When spraying any carburettor cleaner pleaseensure that all rubber components are removedas carburettor cleaners cause damage to therubber parts.

3. It is recommended that the acceleration pumpis completely dismantled before spray is applied.

4. Do not disturb the secondary throttle openingadjuster screw/nut while disassembling, cleaningor reassembling the Carburettor.

5. Ensure that the power valve diaphragm is notdistorted while assembling the power valveassembly.

6. Don’t disturb screws with paint marks as they arefactory set.

SPECIAL TOOLS

Special tools assure three things :

1. Improved workmanship;

2. Speedy execution of jobs for which they aremeant; and

3. Protection of parts and components againstdamage. Special tools are listed below :

a) Volume control screw (adjusting tool)

b) Man jet screw driver.

CARBURETTOR RELATED FAULTS

DO’S AND DON’TS :

1. Exploded view of the carburettor along with listof parts is enclosed for understanding thecarburettor (Fig. 139)

2. Proper sequence of the assembly is to befollowed carefully while dismantling any part inthe carburettor.

Particular care is required while dismantlingPower (enrichment) Valve Assembly. Primary pilotjet and primary & secondary main jets.

3. Make sure that the orifice in the brass pipe usedfor the communication of manifold vacuum to theenrichment valve is not blocked.

When reassembling or replacing the Primary &Secondary Main Jets, ensure that they are notinterchanged; use the jet with same number(stamped on its head) as the one being removed.

The number (size) of the primary main jet shouldbe smaller than that of the secondary main jet.

6. Primary Pilot Jet must be assembled properlywith the lock plate in correct position so that thejet sits properly on the seat. Do not forget toassemble “O” ring in both primary & secondarypilot jets.

68

ENGINEERING

475 SIC PETROL ENGINE

7. Do not remove primary & secondary innerventuries. They are press fitted.

8. Cleaning is recommended with “carburettorcleaner”. Such liquids may not be readly available.Hence Petrol may be used for cleaning, takingthe usual precautions against fire hazards.

9. Damaged gaskets and “O” rings should bereplaced before assembly.

10. Throttle body assembly should not bedismantled. Do not disturb the SecondaryThrottle stop screw since it is factory set.

11. The throttle body assembly is assembled withtwo fixing screws. One screw is white in colourassembled with copper washer and the otherscrew is yellow in colour with regular springwasher. While assembling, do not interchangethese screws and washers.

12. Install the choke cable to the carburettor bodywith the choke knob pulled out about 7mm toensure choke valve returns completely to theoriginal position.

13. Check to ensure that the carburettor solenoidmakes “Clicking” sound when ignition switch keyis turned “ON” and “OFF” (without starting theengine).

14. Solenoid assembly can be removed and re-fixedbut should not be dismantled. While refixing thesolenoid assembly proper care has to be takento assemble the O-ring.

15. If the float is punctured or damaged, petrol willbe present inside the float which can be foundby visual observation. In this case do not attemptto repair the float but replace with genuine sparefloat. While handling the float extra care has tobe taken and the float should not be droppedon the floor.

16. Clean all the parts and jets only with petrol andcompressed air and do not insert wires or drillsinto the jets.

17. Power (enrichment) Valve assembly may beremoved for cleaning. While dismantling, notethe sequence in which each part is assembled.While reassembling, assemble in the propersequence as otherwise the system willmalfunction and cause excessive fuel

consumption. Refer fig. 1

While dismantling and reassembling the FloatChamber Cover, proper care shall be taken notto damage or miss the return pipe “O” ring.

19. A loose stainless steel ball and brass pumpweight positioned in the mixing body pumpoutlet should not be sticky or lost.

20. Pilot screw should not be fully screwed homewith excessive force in order to avoid damageto the tip.

21. The AC Idle up system is factory preset. Screwswith paint mark are not to be disturbed. (if ACfitted)

22. The Float level inspection and adjustment isgiven below :

(a) Disconnect battery negative cable from battery.

(b) Remove air cleaner case.

(c) Disconnect choke cable from carburettor

(d) Disconnect choke lever rod from choke shaftlever.

(e) Remove carburettor upper cover by removingupper cover securing screws and depressionchamber bracket securing screws.

69

ENGINEERING

475 SIC PETROL ENGINE

Fig. 141

(f ) To see if fuel level is properly maintained, floatheight should be maintained, and measuredaccording to the following procedure : Fig. 141

Invert the cover and hold up the float by hand andlower it gradually. Just when float tongue (1) touchesneedle valve (2) measure the distance ‘A’ between thebottom of the float (which is upside in this state) andthe mating surface line of the upper cover and thecarburettor body. If the level is within limits the fuellevel is satisfactory.

The height of the float can be adjusted by thefollowing method :

NOTE :

The gasket must be removed when takingmeasurement of ‘A’. It should be remembered that ahigh float level results in a low fuel level and a lowfloat level results in a high fuel level.

Float height Specification ‘A’ 31-32 mm.

Float

Carburettor

upper cover

FLOAT

CARBURATOR UPPER COVERA

1

2