TRX 2.5 Racing Engine - Blade - #1 By Design

TRX 2.5 Racing EngineOwner’s Manual

Covers Models 5204,

5206, 5207, 5209Traxxas Corporation, 1100 Klein Road, Plano, Texas 75074, Phone: 972-265-8000, Toll-free 1-888-TRAXXAS

Traxxas U.K., P.O. Box 1128, Winterbourne, Bristol BS17-2SH, England, Phone: 44-117-956-1002Internet: www.Traxxas.com, www.ReadyToRun.org

Traxxas CorporationCorporate Headquarters1100 Klein RoadPlano, Texas 75074Phone: 972-265-8000Toll-free 1-888-TRAXXAS

Traxxas U.K.P.O. Box 1128Winterbourne, Bristol BS17-2SH, EnglandPhone: 44-117-956-1002

Internetwww.Traxxas.comE-mail: [email protected]

Entire contents ©2002 Traxxas Corporation. Traxxas, TRX 2.5, Top Fuel, and Ready-To-Race aretrademarks or registered trademarks of Traxxas Corporation. Other brand names and marks are the property of their respective holders and are used only for purposes of identification.No part of this manual may be reproduced or distributed in print or electronic media withoutthe express written permission of Traxxas.

021216

Note: Some photos show the engine equipped with optional accessories, such as the EZ-Start 2system, headers, and engine mounts, that are not included in the engine package. See the endpanel of the engine box for exact contents based on your engine model number.

2

Before You ProceedCarefully read and follow all instructions in this and any accompanying materials to preventserious damage to your engine. Failure to follow these instructions will be considered abuseand/or neglect. Before running your TRX 2.5 Racing Engine, look over this entire manual, andexamine it carefully. If for some reason you decide the TRX 2.5 is not what you wanted, thendo not continue any further. Your hobby dealer absolutely cannot accept a TRX 2.5 forreturn or exchange after it has been run.

Warnings, hints, and cross-referencesThroughout this manual, you’ll notice warnings and helpful hints, identified by the iconsbelow. Be sure to read them!

An important warning about personal safety or avoiding damage to your TRX 2.5 Racing Engine and related components.

Special advice from Traxxas to make things easier and more fun.

Refers you to a page with a related topic.

SupportIf you have any questions about your TRX 2.5 Racing Engine or its operation, call the TraxxasTechnical Support line toll-free at: 1-888-TRAXXAS (1-888-872-9927)

Technical support is available Monday through Friday from 8:30 am to 9:00 pm central time.Technical assistance is also available at www.Traxxas.com. You may also e-mail customersupport with your question at [email protected]. Join thousands of Traxxas R/Centhusiasts in our online community at www.ReadyToRun.org

Traxxas offers a full-service, on-site repair facility to handle any of your Traxxas service needs.Maintenance and replacement parts may be purchased directly from Traxxas, or you can saveshipping and handling costs by purchasing them from your local hobby dealer. 3

4 Safety Precautions

5 Introduction

6 TRX 2.5 Racing Engine Illustrated

7 Terms to Know

11 The Fuel

13 The Air Filter

14 The Carburetor

18 Breaking-in Your TRX 2.5 Racing Engine

22 Tuning the TRX 2.5 forBest Performance

27 Troubleshooting YourTRX 2.5 Racing Engine

30 Maintaining andStoring Your TRX 2.5Racing Engine

33 Index

34 Rebuilding the TRX2.5 Racing Engine

Safety PrecautionsAll of us at Traxxas want you to safely enjoy your new TRX 2.5 Racing Engine. Operate your TRX 2.5sensibly and with care, and it will be exciting, safe, and fun for you and those around you. Failure tooperate your TRX 2.5 in a safe and responsible manner may result in property damage and seriousinjury. The precautions outlined in this manual should be strictly followed to help ensure safeoperation.You alone must see that the instructions are followed and the precautions are adhered to.

Important Points to Remember R/C fuel is dangerous and highly poisonous. Always follow all directions and precautionsprinted on the fuel container.

R/C fuel, especially when in a fuel dispensing bottle, may look like a cool drink to a child. Keepall fuel out of the reach of children at all times. Do not place fuel containers on the groundwhere children can get to them while you are driving.

R/C fuel is flammable. Never allow smoking, sparks, heat or flame in the presence of fuel or fuel vapors.

The engine and exhaust system may become extremely hot during use. Be careful not to touchthe parts, especially when refueling or stopping the engine.

Prolonged exposure to the engine exhaust can be harmful. Avoid breathing the engine exhaust.Always run your TRX 2.5 outdoors, in a well-ventilated area. Never run the engine indoors.

Don’t operate your model at night, or anytime your line of sight to the model may beobstructed or impaired in any way.

Never operate your model in crowds of people or busy pedestrian areas. The TRX 2.5 makesmodels extremely fast, and may cause injury to those unaware of its presence.

The engine can be loud. If the noise makes you uncomfortable, wear ear protection. Beconsiderate of your neighbors by not running your model early in the morning or late in the evening.

Most importantly, use good common sense at all times.▼▼

▼▼

▼▼

▼▼

▼

4

All instructions andprecautions outlinedin this manual should

be strictly followed to ensuresafe operation of your TRX2.5 Racing Engine.

The TRX 2.5 RacingEngine is not intendedfor use by those under

16 years of age without thesupervision of a responsibleand knowledgeable adult.

5

IntroductionThe TRX 2.5 Racing Engine is vastly superior to typicalR/C engines and belongs in the category of specialtyhigh-performance racing engines. It’s the result ofyears of focused engineering development, andthousands of hours of controlled testing and rigorousreal-world running. It offers unprecedented powerand performance that turns ready-to-run into Ready-To-Race®.

The TRX 2.5 Racing Engine takes a total-systemapproach. Each part of the engine, from the air filterto the exhaust tip, is carefully engineered to work inharmony with other engine components. Each part complements the next, to extractmaximum power. The TRX 2.5 is designed to be tolerant of variations in tuning, and to runsuccessfully through a wide range of variable atmospheric conditions, such as changes intemperature, humidity, and altitude.

The TRX 2.5 is manufactured to exacting tolerances and requires a specially-designed break-inprocedure to accomplish the final precision fitting of the internal engine components. It isvery important that you follow the new break-in procedure as closely as possible to achievethe best performance and longest life from your TRX 2.5 Racing Engine. Old style break-inprocedures, such as simply running the engine with a very rich fuel mixture for the first 4tanks of fuel, will not achieve the best results. Follow the steps in this manual.

A routine maintenance schedule is also required to keep the TRX 2.5 in top running condition.Cleaning the air filter after each hour of running is particularly important. Also it is extremelyimportant to perform after-run maintenance on the engine to prevent corrosion of theinternal engine components (see page 30).

Traxxas stronglydiscourages changingor modifying any part

of the TRX 2.5 Racing Engine.Old tech tips and tricks thatmay have boosted the powerof other engines couldseriously diminish theperformance of the TRX 2.5.

There’s more advancedthinking, development andtesting in the stock parts ofyour TRX 2.5 than in manyaftermarket manufacturer’s so-called performance parts. TheTRX 2.5 is already one of themost powerful engines in itsclass and simply will notbenefit from average, low-tech,aftermarket bolt onperformance items.

TRX 2.5 Racing Engine Illustrated

AirFilter

Head Protector

Head (Cylinder head)

Pull Start

Low-SpeedNeedleThrottle

Arm

*ClutchBell

Flywheel

Carburetor

Air Intake

Fuel Intake

High-Speed Needle

Idle SpeedScrew

Crankshaft

Crankcase

6 *not included

OptionalBackplate

7

Terms to KnowYou’ll find these Nitro R/C engine terms throughout this section of the manual.

.15 - .15 or “15” refers to the size of the engine.The TRX 2.5 is .15 cubic inches or 2.5 cubiccentimeters (cc).The name “TRX 2.5” isderived from the cc measurement.

ABC - Abbreviation for aluminum, brass, andchrome. Refers to engine construction thatconsists of an aluminum piston that slides ina chrome-plated brass sleeve.The TRX 2.5uses ABC construction.

Air filter - The air filter sits atop the carburetorand prevents harmful dust and dirt fromentering the engine. Dirt ingestion is thenumber one cause of premature enginefailure so the engine should never be runwithout the air filter in place.

Big Block .15 - A .15 (2.5) engine that uses alarger crankcase size and longer stroke thantypical .15 engines. Generally only used forspecific racing classes.

Break-in - Break-in is the procedure forrunning a brand new engine according tospecific instructions.This correctly preparesthe engine for normal running.The break-inprocedure can be different for differentmakes of engines. Follow the Traxxasdirections for break-in exactly.

Carb - Abbreviation for carburetor.Carburetor - The carburetor atomizes (mixes)

the fuel with the air so that the engine canburn it.There are two types of carburetors,slide carbs and barrel carbs.The TRX 2.5 usesthe superior slide carburetor design.

Clean-out - Cleaning-out is a condition thatoccurs when the engine is accelerating andthe fuel mixture becomes sufficiently lean toallow the engine to continue into its upperRPM power band. Usually characterized by anoticeable decrease in blue exhaust smokeand a dramatic increase in engine speed.

Combustion chamber - The combustionchamber is machined into the bottom of thecylinder head.This is where the glow plugignites the fuel.The shape of the combustionchamber is designed to promote moreefficient burning of the fuel.

Connecting rod - The connecting rod transfers the piston motion to the crankshaft.The TRX 2.5 Racing Engine uses a “knife-edged” connecting rod.The aerodynamic, sharpened edges allowit to “slice” through the pressurized air/fuelmixture inside the crankcase.

Crankcase - The engine “body” that containsall of the running mechanical components.

Crankshaft - The main shaft of the engine thatcontains the rotating assembly.

Cooling fins - The cooling fins are molded intothe cylinder head and crankcase and causeheat to be drawn away from the engine. Heatis removed when it dissipates into the airpassing across the cooling fins.It is important to keep the fins clean of dirt and debris for maximum cooling efficiency.

Cylinder head (head) - The finned aluminumpart on top of the engine that is responsiblefor dissipating most of the engine’s heat.Thecombustion chamber is machined into thebottom of the head.

Dyno - Abbreviation for dynamometer. Aprecise piece of testing equipment thataccurately measures engine power andtorque output over the engine’s entire RPM range.

EZ-Start 2 - Second generation Traxxas on-board electric starting system.The systemconsists of a hand held starter control unitand an on-board gearbox with an electricmotor to spin the engine.The new EZ-Start 2contains many performance and reliabilityimprovements over the first generation EZ-Start 2.

Filter foam - The oiled foam element inside theair filter housing.The filter foam in the TRX 2.5must be thoroughly cleaned and re-oiledafter every hour of run time.

Fit - Usually refers to the fit of the piston andsleeve. If the fit is tight, then the piston will feelvery tight at top of the sleeve and the enginewill have good sealing and compression. If thefit is loose, then compression will be low andthe piston and sleeve should be replaced.

Flame-out - Occurs when the engine stopsrunning at high RPM. Usually the fault of anexcessively lean fuel mixture or glow plugfailure.

Fuel - (10%, 20%) The TRX 2.5 must have model engine fuel to run.Traxxas Top Fuel is recommended. Fuel is sold in quarts andgallons from hobby dealers.The 10% and20% labeling refers to the percentageamount of nitromethane contained in the fuel (see “nitro percentage” definition).

Fuel mixture - The ratio of fuel to air asdetermined by the needle settings of thecarburetor.

Fuel tubing (fuel line) - The thick siliconetubing that carries fuel from the fuel tank to the carburetor.

Glow plug - The glow plug is located in thecylinder head at the top of the combustionchamber. It contains a platinum element thatglows red hot when voltage is applied.Whenthe engine is being started, the heat from theglow plug ignites the fuel mixture and startsthe combustion process.8

Terms to Know

Terms to Know

9

Glow plug driver - This tool clips onto theglow plug and supplies the required voltageto light the glow plug element. It is alsocalled an igniter. EZ-Start equipped enginesdo not require this separate tool.

Header - The aluminum tube that connectsthe exhaust system to the engine exhaustport.The length and diameter of the headermust be carefully selected to extract themost power from the engine.

High-speed needle - Adjusts the carburetorsfuel/air mixture at high RPM.

Idle speed - The speed (RPMs) the engine runs at when the transmitter’s throttletrigger is at neutral.

Idle speed screw - Located on the carburetorbody.This screw adjusts the idle RPM of the engine.

Lean - A running condition where the engineis not getting enough fuel (for the availableair). Symptoms include engine overheating,or the engine runs for a short time and thenstalls, particularly at high speed.This is adangerous condition that should becorrected immediately or it canruin your engine.

Leaning the mixture - Turning either the high speed and/or low-speed needle(s)clockwise to decrease the amount of fuel the engine receives.

Low-speed needle - Needle valve thatcontrols the low-speed fuel mixture.

Needle valve - Valve consisting of a taperedneedle that closes against a correspondingseat to regulate fuel flow.

Nitro - Abbreviation for nitro methane,a component of model engine fuel thatimproves fuel combustion and poweroutput. Nitro also refers to a class ofRC powered by model engines instead of electric.

Nitro content - The amount of nitro methaneused in the fuel. Usually measured as apercentage of the total fuel volume.Traxxasengines are optimized to use 10-20% nitro.30% nitro may be used for racing.

Nitromethane - Nitro methane is acomponent in the fuel that increases powerfrom the combustion process up to a point.Engines are generally optimized to use arange of nitro content for the best power.

O-ring - Rubber “O”-shaped ring used as asealing gasket.

Pipe - Abbreviation for the tuned exhaust pipeon a nitro engine. See “Tuned Pipe”definition.

Piston - The piston is the internal engine partthat is attached to the upper end of theconnecting rod and moves up and down inthe cylinder sleeve.The precise fit between

the piston and the sleeve creates a seal thatallows engine to have the requiredcompression for combustion.

Port - Ports are openings in the sleeve thatallow atomized fuel to enter the combustionchamber and burned exhaust gasses to exit.The shape and location of the ports are alarge factor in controlling the engine timingand power output.

Priming - Manually causing fuel to move fromthe fuel tank up to the carburetor.This issometimes necessary after the engine hasbeen sitting for a long period of time and allthe fuel has drained back to the tank. On aTraxxas model this is done by holding yourfinger over the exhaust tip for one or twoseconds while the engine is starting.

Punch - A term that refers to how quickly themodel responds to throttle input or howquickly it accelerates.

Rich - A running condition where the engine isgetting too much fuel for the available air. Itis better to run an engine slightly rich toincrease engine life. Excessively rich mixturescause the engine to have sluggishperformance with exaggerated blue smokeand unburned fuel coming from the exhaust.

RPM - Abbreviation for revolutions per minute(how many times the engine crankshaftspins in a minute).

Sleeve - Internal engine part that contains the piston.The precise fit between the sleeve and the piston creates a seal thatallows engine to have the requiredcompression for combustion.The sleeve in a TRX engine is made of brass and is then hard-chrome plated.

Slide carburetor - The throttle on a slidecarburetor closes and opens by sliding abarrel in and out of the carburetor body.This type of carburetor is preferred forperformance use because it provides a less restrictive “straight-through” air paththan the barrel carburetor design.

Stall - When the engine stops running, usuallydue to an incorrect fuel mixture setting orrunning out of fuel.

Tuned pipe - The tuned exhaust pipe usuallyconsists of a specially-shaped metal orcomposite chamber with baffles that isdesigned to enhance the power output ofthe engine.

Wear-in - Fitment process that occurs duringengine break-in where internal engine partsdevelop an even more precise matched fitthrough actual use under controlledcircumstances.

WOT - Abbreviation for wide-open throttle.

Terms to Know

10

The Fuel

11

You may use highernitro percentagesthan 20% in certain

circumstances. Call 1-888-TRAXXAS for moreinformation.

The FuelUse the Right FuelIt’s imperative that you use the correct fuel in your TRX 2.5 formaximum performance and engine life. Traxxas Top Fuel should beused to ensure correct engine lubrication, performance, and ease oftuning. Traxxas Top Fuel has been proven in thousands of engines,so you can count on it every day for great performance.

Top Fuel is the only fuel which is 100% certified for use inTraxxas engines.

Traxxas Top Fuel is made with just the right balance of thehighest grade natural and synthetic lubricants to allowexcellent throttle response and the best top-end performance, without sacrificing long-term durability.

All of the components in the fuel are carefully selected from the best materials availableand then custom blended to match the metallurgy and temperature characteristics ofTraxxas engines.

You may use 10% or 20% nitro-content fuel. Use the same percentage all the time; don’tswitch back and forth between 10% and 20% fuel. If you break-in your engine on 20% fuel,then always use 20% fuel.

What about Other Fuels?Can other brands of fuel be used besides Top Fuel? There are other fuels that can providesatisfactory performance; however there could be long-term costs in the form of decreasedengine performance, loss of tuning ease, and shorter engine life.

Everyone has an opinion or a claim to make about fuel. The engineering team at Traxxas spentover 2-years developing the TRX 2.5 Racing Engine. No one knows more about the specific

▼▼

▼

fuel requirements of Traxxas engines than Traxxas engineers. We strongly urge you not to takechances with your engine investment and use the Traxxas fuel made for the TRX 2.5.

Handling the Fuel

Follow all directions and warnings on the fuel can.

Keep the fuel tightly capped at all times. Some components in the fuel can evaporate veryquickly and upset the balance of the fuel.

Do not store unused fuel in the fuel dispenser. Immediately return fresh unused fuel backinto the fuel can.

Do not mix old and new fuel. Never mix different brands of fuel together.

Store the fuel in a cool dry location, away from any source of heat, ignition, or combustion.

Read and follow the safety precautions on page 4 in this manual.▼▼

▼▼

▼▼

The Fuel

12

The Air Filter

13

Clean your air filter afterevery hour of runtime toavoid engine damage,

even if the filter looks clean.

If you use compressed airto dry your air filterassembly, wear safety

glasses and avoid directingcompressed air toward your skin.

The Air FilterThe TRX 2.5 air filter is carefully designed to deliver maximum performance while protectingyour engine from dust and dirt. Use only the supplied filter. You will not improve engineperformance by switching to an aftermarket filter, and you may risk engine damage dueto poor filtration.

The TRX 2.5 air filter assembly consists of 3 pieces:1. A rubber filter base 2. A plastic housing consisting of a permanently assembled mesh cap and body3. An oiled foam element

You must clean the filter after every hour of runtime, even if the filter looks clean. Dust(which is often too fine to see) and dirt constantly move through the filter anytime the engineis running. Even if you can’t see dirt on the filter, it is present inside the foam after any amountof runtime. If you exceed the recommended cleaning intervals, your engine will be damaged.Engine damage or wear due to dirt ingestion is easy to detect, and one of the top causes ofpremature engine failure.

Air Filter Cleaning Instructions1. Remove the air filter from the carburetor bore by pulling

the entire filter firmly to the side to release it. Do not pullstraight up.

2. Disassemble the filter. Pull the rubber base out of the filterbody. With the base removed, the foam element is visiblein the bottom of the filter body. Pull out the foam element.

3. Clean the filter parts by thoroughly washing all threepieces of the filter assembly in hot soapy water(dishwashing detergent works well). Repeat twice.

4. Thoroughly dry the parts with a clean towel or compressed air. Remember to wear yoursafety glasses when working with compressed air.

5. Oil the foam element by saturating it with foam filter oil. Use the supplied Traxxas filter oil(part# 5263) or a high-quality, special-purpose foam filter oil like what is used for high-performance motorcycle and ATV engines. This type of filter oil is available at motorcyclepro-shops. Never run the engine without a properly oiled filter! Apply 30 drops of theTraxxas filter oil evenly to the top, bottom and sides of the filter element (30 total dropsdivided among the 3 surfaces). Squeeze the filter element repeatedly to help spread theoil throughout. The filter element should be evenly colored by the oil. Even color indicatesthat the oil is evenly distributed. Note: Do not use the air filter oil for anything otherthan the air filter. It is not meant to be a lubricant.

6. Reassemble the filter and install it on the engine, making sure the rubber base fits securelyon the carburetor with no gaps or air leaks.

The CarburetorUnderstanding the Carburetor adjustmentsThe carburetor performs several functions. Itcontrols the engine’s speed by restricting theintake of air and fuel into the engine. Itatomizes the fuel (suspends the fuel dropletsin the air) and also controls the air/fuel ratio ofthe mixture entering the engine (how muchair for a given amount of fuel). To help providea better understanding of engine tuning andwhy it’s necessary, the following is a briefexplanation of the air/fuel combustionprocess that takes place inside the engine.In order to create the cylinder pressure that

Air

Fuel

The Air filter

14

The Carburetor

15

results in power, the engine burns the air/fuel mixture. Both air and fuel,in correct amounts, are needed forproper combustion. It is thecarburetor’s job to mix the air and fueltogether (atomize the fuel), in thecorrect proportion for the best possiblecombustion. This is the ideal air/fuelratio required for the engine. The idealair/fuel ratio remains roughly constant.Due to variations in atmospheric conditions (temperature, humidity, altitude etc.) fuel flowadjustment valves (called fuel mixture needles) are required to meter the fuel and maintainthe ideal air/fuel ratio in these ever-changing conditions. For example, colder air is more dense(more air molecules) for a given volume of air and therefore requires more fuel (more fuelmolecules) to maintain the correct air/fuel ratio. Warmer air is less dense (fewer air molecules)and therefore needs less fuel to maintain the correct air/fuel ratio. The tuning needles arethere to adjust how much fuel is made available for the carburetor to mix with the availableair (atomization).

The Fuel Mixture NeedlesThe amount of fuel metered and atomized by the carburetor is controlled by the two mixtureneedles, the high-speed needle and the low-speed needle. The low-speed needle is used tometer the fuel used by the engine at idle and low RPM (part-throttle) engine speed. The high-speed needle is used to meter the fuel when the throttle is open from part throttle to wide-open throttle (WOT). Two needles on the TRX 2.5 provide precise control of the air/fuel ratioacross the engine’s entire RPM range.The maximum possible fuel flow is always controlled by the high-speed needle. It works likethe main water valve on a garden hose. Turn it clockwise to close the valve, counter-clockwise

Dense Air Less Dense Air

to open it. When the throttle is at idle orpartially open, the low-speed needle againmeters the fuel flow at the outlet (needle seat)where the fuel enters the carburetor venturi.This second valve acts like the spray nozzle atthe end of the garden hose in our example.When you accelerate from idle, the throttleopens and the low-speed needle is pulledaway from the needle seat. This allows morefuel to flow with the increased air flow. As thethrottle is increased, the low-speed needle is

pulled completely away from the needle seat leaving it fully open. At that point, fuel meteringis entirely controlled by the high-speed needle. Again, using our water hose example, whenthe spray nozzle at the end of our garden hose is fully open, then the main water valve can beused to adjust how fast the water flows.

The engine’s performance is directly linked to the fuel mixture. Richening the fuelmixture increases the amount of fuel in the air/fuel mixture ratio and leaning the fuelmixture decreases the amount of fuel in the air/fuel mixture ratio.

Slightly lean fuel mixtures deliver stronger, more efficient combustion and more power, butwith less lubrication.

Slightly rich fuel mixtures deliver cooler running and more lubrication but with slightlyless power.

Tuning the engine means finding the perfect balance between the two; excellent power tomeet your needs while maintaining good lubrication for long engine life. The optimal fuelmixture setting is rich to provide a safety margin against having a lean condition if somevariable changes (such as the temperature from one day to the next).

▼▼

Water Valve(Controls Overall Flow)

High Speed Needle

Water Nozzle(Controls Fine Flow)

Low Speed Needle

See Tuning the TRX 2.5for Best Performance onpage 22 for complete

information on adjusting theair/fuel mixture and idle speed.

If your factory preset carburetoradjustments have

been tampered with, use thefollowing settings: set the low-speed needle so that the screwhead is flush with the end ofthe slide. Set the high-speedneedle to 4 turns out fromclosed. Always use the factorysettings for initial starting.Only use these settings whenthe factory settings have been lost.

The Carburetor

16

The Carburetor

17

General fuel mixture settings aremeasured by the number of turns theneedles are turned out from fullyclosed. The fuel mixture settings havebeen pre-set from the factory totypical break-in settings. Do notreadjust your carburetor from thefactory settings until after the engineis started and running, and you havebeen able to observe the enginerunning to assess what minor adjustments may be required to compensate for fuel,temperature, and altitude. Adjustments are usually made in 1/8 or 1/16-turn increments.

The Idle Speed AdjustmentThe idle speed screw controls the closed position of the throttle slide. When the throttle servois in its neutral position, the throttle slide should be stopped against the idle adjustmentscrew. Always use the idle speed adjusting screw to control engine idle. Do not use thethrottle trim on the transmitter to adjust idle speed. The idle speed should be set as low aspossible and still maintain reliable running.

LeanRich

Breaking-in Your TRX 2.5 Racing EngineThe TRX 2.5 uses a ringless, aluminum-brass-chrome (ABC) piston/sleeve construction. Thistype of engine design relies on a very precise running fit between the piston and sleeve forcylinder sealing. Engine break-in is necessary to allow the piston and sleeve to developan extremely precise fit and optimum cylinder sealing. Therefore, proper engine break-in is critical to achieving the fastest, most reliable engine performance.

Allow yourself about 1 to 11/2 hours to complete the break-in procedure. The engine break-inperiod will take 5 tanks of fuel. The break-in time is not the time to impress your friends withyour new TRX 2.5 Racing Engine. You must wait until the engine is fully broken-in beforeattempting sustained high speed running. Patience and careful attention during break-inwill reward you with the best-performing TRX 2.5 possible.

During break-in, your engine may appear to malfunction with symptoms like stalling,inconsistent performance, and fouled glow plugs.These are simply the normal “break-in pains”engines sometimes go through.They will disappear once your engine is fully broken in. Manyowners report not experiencing any of these symptoms with the TRX 2.5. We recommendreplacing the glow plug with a new one after the engine break-in procedure.

Engine Break-in ProcedureThe focus during break-in is to vary and limit the engine speed. This will be accomplished byaccelerating and stopping at different rates for the first 5 tanks of fuel. As the engine begins tobreak-in, the duration and intensity of the acceleration will gradually increase. Sustainedhigh-speed running is not permitted until the 6th tank of fuel. Perform the initial break-inon a large, flat, paved surface. Apply all throttle and braking actions gently. Abruptacceleration or braking could cause the engine to stall unnecessarily.

Special break-in fuels are not recommended. Use the same fuel you plan to use everyday.If possible, avoid breaking-in the engine on extremely hot or cold days.Pay careful attention to the fuel level. Do not allow the fuel tank to run completely empty.▼

▼▼

See Important Points toRemember on page 4for other precautions.

Never run your modelindoors. Since the TRX 2.5 Racing Engine

exhaust fumes are harmful,always run your modeloutdoors, in a well-ventilatedarea.

Your TRX 2.5 RacingEngine doesn’t usuallyrequire priming. If you

do need to prime your engine,watch the fuel line carefully toavoid flooding your engine.See page 30 for informationon clearing a flooded engine.

Your carburetor is pre-set at the factory togive the correct air-to-

fuel ratio and idle speed forengine break-in. Do not adjustthe carburetor unless youobserve a poor runningcondition that requirescorrection.

Breaking-in Your TRX 2.5 Racing Engine

18


19

An extremely low fuel level causes the mixture to run too lean. This could result in aburned glow plug or extremely high engine temperatures.Keep extra glow plugs handy (Traxxas part #3231). The break-in process can causedeposits to form on the plug leading to plug failure.Follow the instructions exactly for each of the first 6 tanks of fuel.

Starting Your TRX 2.5 Racing Engine for the First TimeBefore you start your TRX 2.5 Racing Engine for the first time, make sure you have read allinstructions and precautions in this manual. Pay close attention to the tank-by-tank break-ininstructions in the next section, and make sure you have read and understood them beforeyou run your engine.

Your engine must be at room temperature (70°F or 21° C) or above the first time you start it.If it’s cooler than room temperature outside, keep your TRX 2.5 Racing Engine indoors untilyou’re ready to start it, then take it outside.1. Turn on the radio system .2. Make sure the throttle is in the idle position.3. Pull the starter handle with quick, short, continuous pulls, and watch for fuel moving through

the fuel line up to the carburetor.Watch closely! The fuel moves very fast. If the fuel doesn’tmove through the line within 5 seconds, prime the engine by briefly (one or two seconds)covering the exhaust outlet until the fuel is just visible in the carburetor fuel line. Watchcarefully! If the engine is primed too long, it will flood with fuel and stop turning.

5. Once fuel reaches the carburetor, the engine should quickly start and idle.6. Proceed with the engine break-in.If your engine doesn’t start, see Troubleshooting Your TRX 2.5 Racing Engine on page 27.

▼▼

Tank 11. Drive the model with the body off.2. Driving procedure: Gently pull the throttle trigger to 1/4 throttle over a 2-second count. Then

gently apply the brake to stop. Count the two seconds out while accelerating: one thousandone, one thousand two, and then stop. Operate the throttle trigger as smoothly as you can.Repeat this starting and stopping procedure until the first tank of fuel is nearly empty.

3. Look for thick blue smoke exiting the exhaust outlet. If there is no smoke, richen the high-speed needle 1/4 turn, by turning the needle counterclockwise.

4. When the fuel tank is nearly empty, shut off the engine by pinching the fuel line connected to the carburetor.

5. Let the engine cool for 15 minutes.Note: If at any point the engine cuts out or stalls during gentle acceleration, richen the high-speed needle 1/4 turn by turning the needle counterclockwise.

Tank 21. From tank 2 forward, your model should be driven with the body on.2. Driving procedure: Gently pull the throttle trigger to 1/2 throttle over a 2-second count.

Then gently apply the brake to stop. Count the two seconds out while accelerating: onethousand one, one thousand two, and then stop. Repeat this starting and stoppingprocedure until the second tank of fuel is nearly empty.

3. When the fuel tank is nearly empty, shut off the engine and let it cool for 15 minutes.

Tank 31. Driving procedure: Gently pull the throttle trigger to 1/2 throttle over a 3-second count.

Then gently apply the brake to stop. Count the three seconds out while accelerating: onethousand one, one thousand two, one thousand three, and then stop. Repeat this startingand stopping procedure until the third tank of fuel is nearly empty.

2. As the engine loosens, the idle speed may increase and cause the model to try to creepforward when stopped. Reduce the idle speed by turning the idle adjustment (see page 24)on the carburetor counterclockwise.

3. When the fuel tank is nearly empty, shut off the engine and refuel.You do not need to let theengine cool between tanks from this point on.

As you gainexperience in thehobby, you may

discover that many peoplehave differing opinions onwhat is the proper procedureto break-in a model engine.Only use the Traxxas break-inprocedure. Other break-inprocedures could result in aweak, damaged, or otherwisepoor performing engine. Theprocedure outlined here wasextensively tested and provento yield better performingengines than other “common”break-in methods. Even if youhave years of experience usingmodel engines, please do notignore this caution!


20


21

Tank 41. Driving procedure: Gently pull the throttle trigger to full throttle over a 3-second count.

Then gently apply the brake to stop. Count the three seconds out while accelerating: onethousand one, one thousand two, one thousand three, and then stop. Repeat this startingand stopping procedure until the fourth tank of fuel is nearly empty.

2. Apply the throttle gradually! Your finger should not reach full throttle until the end of thethree-second count.

3. Keep your driving smooth and consistent.4. When the fuel tank is nearly empty, shut off the engine and refuel.

Tank 51. Driving procedure: Gently pull the throttle trigger to full throttle over a 3-second count,

hold for 2 more seconds, and then gently apply the brake to stop. Count the five secondsout while accelerating. Repeat this starting and stopping procedure until the fifth tank offuel is nearly empty.

2. When the fuel tank is nearly empty, shut off the engine and refuel.

Tank 6During the sixth tank of fuel, the engine can be tuned for general performance use. Proceed tothe next section in this manual.

Tank12345

Throttle1/41/21/2FullFull

Time2 Seconds2 Seconds3 Seconds3 Seconds5 Seconds

Cool15 Minutes15 Minutes

---

BodyOffOnOnOnOn

NotesApply throttle gradually.Apply throttle gradually.Reduce idle speed if necessary.Keep your driving consistent.Accelerate over 3 second count,hold for 2 seconds.

Tuning the TRX 2.5 for Best PerformanceThe engine’s performance depends on the fuel mixture. Turn the mixture needles clockwise tolean the fuel mixture and counterclockwise to richen it. Leaning the fuel mixture will increaseengine power up to the engine’s mechanical limits. Never run the engine too lean (notenough fuel flow). Never lean the engine until it begins to cut-out or stall. Leaning theengine beyond the safe allowable limits will result in poor performance and almost certainengine damage. Indications of an overly lean mixture include:

Cutting out or sudden loss of power during acceleration. Overheating (temperature beyond 270° F at the glow plug).Little or no blue smoke coming from the exhaust.

If any of these conditions are present, stop immediately and richen the high speed mixture1/4 turn. The engine will probably be slightly rich at that setting and you can then retune forperformance. Always tune for performance by starting rich and moving leaner toward theideal setting. Never try to tune from the lean side. There should always be a light stream ofblue smoke coming from the exhaust.

Before you begin tuning, the engine should be warmed up to its normal operatingtemperature and running slightly rich. All final tuning adjustments must be made to theengine at its normal operating temperature. You can tell the engine is running rich by notingany of the following:

Sluggish acceleration with blue smoke coming from the exhaust.There is unburned fuel spraying from the exhaust tip.Leaning the high-speed fuel mixture increases performance.▼

▼▼

▼▼

▼

When adjusting thelow-speed fuel mixture,it is very important to

make several high-speed runswith your model betweenadjustments to clear out anyexcess fuel. Perform the pinchtest immediately after. If theengine is allowed to idle for along period of time, it could“load up” with fuel and give youan inaccurate measurementfrom your pinch test.

For your convenience,the low-speed needlehas a positive stop that

prevents it from being overtightened and damaging theneedle and seat. This alsoprovides an easy way to gaugehow many turns out fromclosed the low-speed needleadjustment is set to.

Tuning the TRX 2.5 for Best Performance

22


23

When tuning forperformance, watchclosely to notice when

there is no longer any increasein speed or power when thehigh-speed mixture is lean. If you lean the high-speedmixture to the point that theengine cuts-out, hesitates, orstalls, you are well into thedanger zone and enginedamage is likely. Richen thehigh-speed needle 1/4 turnand retune.

High-Speed Fuel Mixture AdjustmentWith the engine warm and running at a richsetting, gradually lean the high-speed fuelmixture in 1/16 turn increments. Make severalhigh-speed passes with the your model aftereach adjustment to clear out the engine andnote any change in performance. The TRX 2.5is extremely powerful. Remember to applythe throttle gradually to prevent loss ofcontrol. Continue this procedure until there isno longer any performance improvement. If anyone of the following conditions occurs, thefuel mixture is already past the maximum safelean setting:

1. The engine begins to cut out at highspeed (Danger!)

2. There is a sudden loss of power duringacceleration (Danger!)

3. The engine begins to overheat. Symptomsof overheating include:

Steam or smoke coming from the engine (not exhaust)Hesitation or stalling during accelerationPopping or clattering sound when decelerating (detonation)Fluctuating idle speedTemperature measurement above 270° F at the glow plug

Richen the high-speed needle at least 1/4 turn counterclockwise and retune for performance.

▼▼

▼▼

▼

Low-Speed Fuel Mixture AdjustmentThe low-speed mixture is always set after the high-speed needle is correctly adjusted.The low-speed mixture will be set using the pinch test.

1. Once the engine is warm, do several high-speed runs to confirm that the high-speedneedle is set correctly.

2. Bring the vehicle in and pinch closed the fuel line going into the carburetor. The engineshould run for 2-3 seconds, speed up, and then die.

3. If the engine runs longer than 3 seconds, then lean the low-speed needle 1/16 turn,make several more high-speed runs, and retest.

4. If the engine dies immediately without speeding up, then richen the low-speed needle1/8 turn, make several more high-speed runs, and retest.

When the low-speed needle is set correctly, the engine’s throttle response should be very quick.

Idle Speed AdjustmentOnce the high and low-speed mixtures have been set, reduce the idle speed to the minimumreliable idle speed. Remember, this adjustment should be made while the engine is running atnormal operating temperature.

1. Turn the throttle trim on the transmitter so that the brakes are applied. This ensures thatthe throttle slide is resting against the idle adjustment screw.

2. If necessary, remove the air filter to gain access to the idle adjustment screw.3. Turn the screw counterclockwise to reduce the idle speed, or clockwise to increase it.

The idle speed should be set as low as possible while still maintaining reliablerunning characteristics.

4. Reset the throttle trim on the transmitter


24


25

Check the Traxxaswebsite for additionalinformation on base

line settings for your area.

Fine-Tuning the CarburetorAfter fine-tuning your TRX 2.5 Racing Engine at the end of the break-in procedure, no majoradjustments to the fuel mixture are usually necessary. Make note of the temperature,humidity, and barometric pressure at the time you finished fine tuning your carburetor.Current weather conditions can be found online from national websites, local TV newswebsites, and television. This information will be considered your baseline setting. You mayneed to adjust your carburetor needles to compensate for changes in temperature andbarometric pressure (air density) from day to day. Generally, you’ll need to richen the fuelmixture when the weather is colder than your baseline temperature and the air density ishigher. Lean the fuel mixture when weather is warmer than your baseline temperature andthe air density is lower. The chart below provides general guidelines on how weatherconditions affect air density when they move higher or lower than your baseline setting (seepage 14 for detailed info on how air density affects mixture settings).

If the...Humidity

Pressure (barometer)

Temperature

Altitude

Nitro %

is..LowerHigherLowerHigherLowerHigherLowerHigherLowerHigher

then the air density is...Slightly more denseSlightly less denseLess denseMore denseMore denseLess denseMore denseLess dense

adjust (correct) the fuel mixture to be...Slightly richerSlightly leanerLeanerRicherRicherLeanerRicherLeanerLeanerRicher

Tuning the Engine by TemperatureThe following procedures require an optional infraredtemperature probe or on-board temperature gauge (Traxxason-board digital temperature gauge, part#4090). Enginetemperature can be used as an effective tuning aid when youunderstand the relationship between engine temperature andambient temperature.

The engine operating temperature, when tuned for maximum performance, will varyaccording to atmospheric conditions. The atmospheric condition that has the most influenceon engine temperature is air temperature. Expect the engine temperature to vary almost indirect proportion to atmospheric temperature.Assuming you tuned the engine for the same maximum performance each day, the enginewill run about twenty degrees hotter when it’s ninety degrees outside than it would inseventy-degree weather. For this reason, we cannot give you a definitive temperature rangethat indicates the best possible engine tuning.The temperature gauge can aid you in tuning by giving you a relative indication of how youradjustments are affecting the engine and by preventing you from exceeding maximumengine temperature. For example, as you lean the fuel mixture, the engine performance willincrease along with the temperature. If you continue to lean the fuel mixture and thetemperature increases but the engine performance does not change, then you have exceededthe maximum safe lean setting.

Even if it’s 100°F outside, you should be able to tune for maximum performance. Try to keepyour engine from exceeding 270°F when measured at the glow plug. If tuning for maximumperformance results in engine temperature exceeding 270°F, try to increase airflow to theengine by cutting out the windshield. If the engine temperature still cannot be kept below270°F, richen the high-speed needle slightly.


26

Troubleshooting Your TRX 2.5 Racing Engine

27

Troubleshooting Your TRX 2.5 Racing EngineThe following section addresses some very basic engine and radio questions you may have aboutyour TRX 2.5 Racing Engine. Most questions arise from simple user errors or minor adjustments thatare easy to correct. If you can’t find a solution for your TRX 2.5 Racing Engine here, then visit ourweb site at www.Traxxas.com and click on the Customer Support menu. There you will find a muchmore extensive and detailed online troubleshooting area. In addition, you may call TraxxasCustomer Service at 1-888-TRAXXAS (outside the US call 972-265-8000).

Engine spins but will not start:

Make sure your glow plug igniter is fully charged and connecting properly to the glow plug.If the igniter is fully charged, then replace the glow plug. It is normal for glow plugs to require

periodic replacement. Only use Traxxas heavy-duty long glow plugs (part #3231).

Check to make sure the fuel is getting to the carburetor. Remove the fuel line where it connectsto the carburetor to see if there is fuel in it. If not, you may need to prime the engine. Reconnectthe fuel line and then refer to page 18 for instructions on priming the engine.

Check your fuel mixture settings. It may be necessary to adjust the fuel mixture if the outsidetemperature or barometric pressure has changed significantly since the last time the engine was run (see Fine Tuning the Carburetor on page 25). Turn the high-speed needle out(rich/counterclockwise) 1/4 turn, hold the throttle trigger at about 1/2 throttle and try again to start the engine. Once started, retune the engine for performance (see page 22).

The engine could be worn. If the fit between the piston and sleeve is loose, compression isreduced and the engine will be difficult to start when it is warm, and may tend to stall whenrunning and when the throttle is closed suddenly to idle. Engine life depends on many factorsincluding fuel type, air filter maintenance, needle settings, and how the engine was used. Forexample, if the engine was allowed to ingest dirt from lack of air filter maintenance or runningthrough water, then the internal engine components could wear out extremely fast.

▼▼

▼▼

Engine will not spin (pull start or electric starter will not turn the engine):

The engine could be flooded. If too much fuel accumulates in the combustion chamber at start up,the engine will hydraulically lock. Follow the procedure on page 29 for clearing a flooded engine.

Check for binding at the engine flywheel. If you are not able to turn the engine by hand, theengine could be flooded, there could be binding in the clutch system, or there could be internalengine damage. See page 29 for info on clearing a flooded engine and releasing a stuck piston.(Note: It is normal for the engine to be extremely tight and hard to turn when the piston reachesthe top of the compression stroke.)

Engine extremely sluggish, hard to start, and will not idle during tank 1 of the break in:

It is possible that the factory adjusted break-in settings on your carburetor are too rich for yourgeographic location, atmospheric conditions, or fuel brand. Extremes in temperature, humidity,barometric pressure, and altitude can’t always be accounted for with a single high-speedneedle setting. The symptoms described above can occur when the air density is very low suchas in high mountainous elevations, and extremely cold temperatures. Under these conditions,lean the fuel mixture slightly, 1/8 turn, to see if there is any improvement in starting and idling.Only lean the fuel mixture just until the engine will run and idle reliably and then proceed with the break in.

The contents of different brands of fuel (other than Traxxas Top Fuel) in combination withextreme atmospheric conditions can also make the factory preset break-in settings too richand cause the symptoms described above. Again, try leaning the fuel mixture slightly, 1/8 turn,to see if there is any improvement in starting and idling.

Engine performance sluggish:

Engine performance depends mostly on the fuel mixture settings and how they compensate forthe current atmospheric conditions. Before you suspect other failures with the engine, richen thehigh-speed needle at least 1/4 turn and then retune the engine for performance (see page 22).

▼▼

▼▼

▼


28


29

Try a new Traxxas #3231 glow plug. Sometimes a glow plug will work well enough to start the engine but not be able to deliver the engine’s full performance potential.

If the fuel mixture seems to be set correctly, make sure the fuel is fresh. If the fuel is old, or wasleft uncapped for a long period, then some of the important fuel components could haveevaporated. Try new, fresh, Traxxas Top Fuel

Check to make sure there is no binding in the driveline that would cause excessive loads on the engine.

Clearing a Flooded Engine:If the engine is primed for too long during startup, then it can become flooded with fuel. When theengine is flooded it will no longer turn due to excess fuel in the combustion chamber preventingupward movement of the piston. Use the following procedure to clear a flooded engine.

1. Remove the glow plug and gasket with the glow plug wrench supplied with your model. A 5/16nut driver will also work.

2. Turn the model upside down.3. Pull the starter handle several times to clear the engine of excess fuel.4. Turn the model over and reinstall the glow plug and gasket.5. Do not prime the engine. Apply 1/2 throttle and pull the starter. The engine should

start immediately.

Piston Stuck at Top Dead Center (TDC):A new engine will typically have a tight fit between the piston and the top of the sleeve. This is atapered fit. The fit should not be too tight to start the engine. If the engine is stuck at TDC, then use a pair of needle nose pliers to grasp the flywheel from the bottom of the engine. Rotate the flywheelcounter-clockwise when viewed from the front of the engine.You should see the flywheel turn andyou should feel the piston become unstuck from the sleeve.

▼▼

▼

Maintaining and Storing Your TRX 2.5 Racing Engine

30

If the engine is worn ordamaged enough torequire replacing the

piston, sleeve, or connectingrod, consider exchanging yourold engine for a brand newengine under the terms of theTraxxas Lifetime EngineReplacement Plan (ERP). Itcould save you time and effort.Details are in your model’sdocumentation package or onour website.

Maintaining and Storing Your TRX 2.5 Racing EngineTRX 2.5 Racing Engine requires timely maintenance in order to stay in top running condition.Neglecting the maintenance could allow dirt, deposits, and moisture to build up inside the engine leading to internal engine failure. The following procedures should be taken very seriously.

After each hour of running:

Clean and re-oil the air filter.The instructions for this procedure are on page 14. We cannotstress enough the value of cleaning your air filter at the scheduled intervals. Do not neglectyour air filter maintenance!

Clean the outside of the engine of accumulated dirt, oil, and grime. Accumulated grime willdecrease the engine’s ability to cool itself.

After each running session:

Perform after-run maintenance on the engine.This clears the engine of destructive moistureand other corrosive deposits. This is extremely important for the life of the engine. See page32 for after-run maintenance procedures.

Inspect the vehicle for obvious damage or wear. Look for:1. Loose or missing screws2. Cracked, bent, or damaged parts 3. Cut or loose wiring 4. Cut or kinked fuel lines5. Signs of fuel leakage

Inspect the gears for wear, broken teeth, or debris lodged between the teeth.

After-run ProcedureYou must perform after-run maintenance on your Traxxas engine whenever the model will bestored for longer than a few hours.Taking the time to prepare your engine for storage will rewardyou with longer engine life, easier starting, and better performance.

▼▼

▼▼

▼

When a nitro engine is shut off, some excess unburned fuel remains in the engine.The methanol inmodel engine fuel is hygroscopic, which means it easily attracts and absorbs moisture.Thismoisture can cause rust and corrosion on the steel engine parts (crankshaft, bearings, wrist pin andstarter shaft) if the fuel is not removed from the engine.There are after-run oil products availablefrom your hobby dealer or you can use WD-40™, a common household lubricant.To ensure yourTRX 2.5 Racing Engine is protected from internal corrosion, use the following procedure:

1. Whenever possible, shut off the engine by pinching the fuel line closed.This allows most ofthe excess fuel to be consumed by the engine. Be sure the throttle is in the idle position.Youmay have to pinch the fuel line closed for several seconds before the engine stops.

2. Completely empty the fuel tank. Use your fuel-dispensing bottle to suck out the old fuel.Do not mix the old fuel with your fresh fuel supply. If you leave fuel in the tank, transporting or handling your model may cause fuel to run into the engine.

3. With the fuel tank empty and the throttle at the idle position, try to start the engine.The engine will most likely start and run for a few seconds as it uses up any fuel remaining in the engine and fuel lines.

4. Once the engine stops, clean the outside of the engine with compressed air or spray motorcleaner. Once the engine is clean and dry, remove the glow plug power wire, glow plug, andair filter.

5. Open the throttle fully and spray a one-second burst of WD-40™ into the carburetor andinto the glow plug hole (Caution! Wear safety glasses to prevent spray from getting into

your eyes).6. Place a rag or paper towel over the engine to catch any WD-40™ that may come out the

carburetor or glow plug hole.7. Pull the starter handle continuously for about 10 seconds.8. Remove the rag or paper towel and repeat steps 5–7 two more times.9. Clean and re-oil the air filter so it will be ready for use next time. See page 13 for air filter

maintenance instructions.10. Replace the glow plug and reinstall the air filter. 31


The TRX 2.5 isdesigned to be easilyrebuilt. Critical engine

components such as thecrankcase, crankshaft, andengine bearings are made toextremely high qualitystandards and should undernormal circumstances outlastmultiple sets of pistons,sleeves, connecting rods, andwrist pins (reciprocatingassemblies). It could be moreeconomical for you to continueto use your good bearings andcrankshafts, and simplyreplace the reciprocatingassembly as needed. Engineassembly is not difficult andreplacing the reciprocatingassembly does not require anyspecial tools or skills.

Denatured alcohol(available from homecenters and paint

supply stores) in a spray bottle is an extremely effective cleaner.Be sure to wear safety glassesand gloves when working withdenatured alcohol.

Other periodic maintenance:

Piston/sleeve: The life of the piston and sleeve will vary greatly with how the enginewas used and maintained.The piston and sleeve should be replaced when they nolonger seal effectively (loss of compression). Symptoms include the engine being difficultto start when warm, stalling when warm, and stalling when throttle is suddenly closed toidle. Replace the wrist pin and G-clip whenever the piston and sleeve are replaced.

Connecting rod: The connecting rod should be replaced when the piston and sleeveare replaced or after three gallons of fuel, whichever comes first. Also replace the pistonwrist pin and G-clip whenever the connecting rod is replaced. As with other internalengine components, the connecting rod’s life depends on the engine’s usage and thequality and frequency of the engine’s maintenance.

▼▼


32

Fun fact: WD-40™

stands for “waterdisplacement attempt

#40.” The WD-40™ productused today was the successful40th attempt at creating awater-displacing lubricant.WD-40™ was the lab test label.

Be sure to followproper maintenanceand storage

procedures to avoid damage toyour engine.

Don’t put the fuel fromyour tank back intoyour fuel jug. Dispose

of it properly, following city orcounty regulations.

Always wear eyeprotection when usingcompressed air or

spray cleaners and lubricants.

Index

33

.15 ........................................................7ABC ......................................................7After-run Procedure....................30Air Filter ............................6, 7, 13, 14

aftermarket filter ........................13cleaning ........................................13filter foam ......................................8oiling ..............................................14

Air Intake............................................6Backplate ..........................................6Big Block .15 ....................................7Break-in..........................7, 18, 19, 20

Tank 1 ............................................20Tank 2 ............................................20Tank 3 ............................................20Tank 4 ............................................21Tank 5 ............................................21Tank 6 ............................................21

Carburetor ........6, 7, 14, 15, 16, 17adjustments ................................14fine-tuning ..................................25mixture needles ..........................15slide ................................................10

Clean-out ..........................................7Clutch Bell..........................................6Combustion chamber ..................7Connecting rod ..............................7Cooling fins ......................................7Crankcase ......................................6, 8Crankshaft ....................................6, 8Dyno ....................................................8EZ-Start ..............................................8Fit ..........................................................8Flywheel ............................................6

Fuel ........................................8, 11, 12fuel mixture..............................8, 16handling ......................................12nitro-content ..............................11other brands ................................11Top Fuel ........................................11

Fuel Intake ........................................6Fuel tubing........................................8Glow plug ..........................................8Glow plug driver ............................9Head ................................................6, 8

protector ........................................6Header ................................................9High-Speed ........................6, 16, 23

high-speed needle....................6, 9Idle Speed..............9, 17, 18, 21, 24

idle speed screw ........................6, 9Internet ..............................................2Lean......................................................9Low-Speed ..............6, 9, 16, 22, 24Maintaining and Storing ......................30, 31, 32Modifying ..........................................5Needle valve ....................................9Nitro ....................................................9O-ring ..................................................9Pipe ......................................................9

tuned..............................................10Piston ..................................................9Port ....................................................10Priming......................................10, 18Pull Start ............................................6Punch................................................10Rich ....................................................10

RPM....................................................10Safety ..................................................4Sleeve................................................10Stall ....................................................10Starting ............................................19Support ..............................................3Throttle Arm ....................................6Traxxas Lifetime EngineReplacement Plan........................30Troubleshooting ............27, 28, 29Tuning ..............................................22

by temperature ..........................26Wear-in ............................................10WOT ..................................................10

These instructions are for the rebuildingof the Traxxas TRX 2.5 engine once theengine has been removed from thechassis. These instructions wereperformed on an engine equipped withthe EZ-Start 2 electric starting system.Engines equipped with pull starters orbackplates (without starter) are similar. It is very important to clean the exteriorof the engine and EZ-Start systemthoroughly before disassembly. Theseinstructions show you how to replace theentire internal reciprocating assembly.

Rebuilding the TRX 2.5 Racing Engine

The following instructions are for enginesequipped with IPS crankshafts using Traxxasclutch components. For multi-shaft™

crankshafts in non-Traxxas applications,follow the manufacturer’s directions forclutch installation removal.

2. Remove the 5.0mm E-clip from thecrankshaft (Nitro 4-Tec owners will need toremove the 3x10CS screw) and slide the5x8x0.5TW with the clutch bell off of the crankshaft (Nitro 4-Tec owners willneed to slide two 5x8x0.5TW off the pilotshaft.) Caution: It’s important to use eyeprotection when removing the E-clipfrom the shaft to prevent the clip fromcausing an injury. Pull the clutch shoesoff of the flywheel pins.

Remove the flywheel nut from thecrankshaft using an 8mm socket (202)and disconnect the flywheel from thecrankshaft by lightly tapping the back of the flywheel with a rubber or plastic mallet.

Place a small flat blade screwdriver intothe slot of the split cone washer and twistslightly to loosen the split cone from thecrankshaft (203). Slide the split conewasher off of the crankshaft. The engine is now ready to be rebuilt (204).

1. Start by removing the exhaust pipeand header from the engine by removingthe two 3x15CS screws (102 & 103).

Remove the three 3x12BCS screwsthat secure the EZ-Start (or pull start)assembly to the engine and separate thedrive unit from the engine (104). If yourengine is equipped with a backplate,proceed to step 2.

101

102

103

104

201

203

204

34

202

35

3. Remove the glow plug from thecooling head and discard the plug.The glow plug should be replacedwith a new one anytime the engine is rebuilt.

Remove the four 3x6CS (3x6BCS onengines equipped with non-starterbackplate) screws from the backplate ofthe engine and pull the backplate fromthe crankcase (301).

Remove the cooling head from the engine case by removing the five3x12CS head bolts (302). Be carefulnot to lose or damage the copperhead gasket. If the head gasket isdamaged, replace it with a new one.

4. Locate the bottom of the sleevethrough the rear opening of thecrankcase. Press the bottom of thesleeve upward with a plastic orwooden stick (401), this is to preventinternal damage to the crankcase.The sleeve should slide up and out of the crankcase (402). (Note: If thesleeve does not slide out of thecrankcase with reasonable effort,slightly warm the crankcase with ahair dryer or heat gun to about 130° F.The sleeve should slide out easily at

this temperature. Use gloves toprotect against burns. ) Rotate thecrank to where the rod and piston arelocated at TDC (top dead center)(topof the piston’s stroke)(403).

Gently pull on the bottom of theconnecting rod with needle nosepliers, sliding the rod off of the crankpin (403). Be careful not to damagethe connecting rod if the rod is being reused.

The rod and piston assembly willexit the top of the crankcase (404).

5. Push the end of the pilot shaft through the crankcase. Thecrankshaft should exit the rear of the crankcase (501). Loosen the 3.0NLjust below the base of the carburetor(502). Slide the carburetor up and outof the crankcase (503). Now thecrankcase is ready to be flushed clean and inspected.

301

302

401

402

403

404

501

502 503


6. Flush the crankcase and bearings out with out with denatured alcohol orelectric motor spray. Dry the crankcasewith compressed air (601).Caution: Do not let the compressed airspin the bearings and always use eyeprotection when using compressed air.

Inspect the crankcase and bearingsfor damage or missing parts. Make surethat the bearing cages are not brokenand check for corrosion inside of thecrankcase. The bearings should feelsmooth and have little play. Make surethe bearings spin freely and that thereare no particles or grit in them. Replacethe bearings if there are any signs ofdamage. Inspect the exhaust o-ringgasket and the backplate o-ring gasketfor tears (602). Replace these o-rings if needed.

7. Apply a few drops of machine oil orafter-run oil to the bearings. Inspect thecrankshaft for corrosion and also checkfor scratches or score marks around theintake port of the crankshaft (see arrow).Check the crank pin for wear (701). Theconnecting rod should fit and rotatesmoothly on the crank with no playbetween the rod and the crank pin. Ifthere is play between a NEW connectingrod and the crank pin then the crank pinis worn and the crankshaft will need tobe replaced.

Important: Do not reuse a damaged or worn crankshaft.This will dramaticallyshorten the life of your rebuilt engine.If there are damaged or worn parts beyondthe piston, sleeve and connecting rod it maybe best to take advantage of the TraxxasEngine Replacement Program.8. Slide the crankshaft back through thecrank bearings until it stops. Inspect thecarburetor o-rings for damage and therubber throttle arm boot for tears (801).Note: On carburetors with a lower o-ring (as shown, arrow), it is necessary to replace it(part #5234) when the carburetor is removed.The o-ring can be reused on models with thebottom o-ring in the crankcase.

Unscrew the hi-speed needle all the wayout of the needle housing (802) and flush outthe hi-speed needle housing and thecarburetor body with denatured alcohol orelectric motor spray. Use compressed air todry the components. Remember: Alwayswear safety glasses when using compressedair to prevent injury. Reinstall the hi-speedneedle into the needle housing and returnthe mixture setting back to the factoryrecommended break-in setting (four turnsout from fully closed).

Carefully insert the carburetor into the crankcase until fully seated. Whilepressing the carburetor firmly into thecrankcase, tighten the pinch bolt (803).This process ensures that the upper O-ring forms a good seal between thecarburetor and the crankcase.

601

602

701

801

802

803

36


10. Lube the outside of the piston with after-run oil and make sure thecrank is at BDC (bottom dead center),then slowly lower the sleeve until It isjust above the piston. Rotate the crankslowly to bring the piston into thesleeve. If there is any resistance, stop!Repeat until the piston movessmoothly into the sleeve. Bring thepiston close to TDC, then push thesleeve in fully. Important: The slot (inthe lip) at the back of the sleeve mustkey into the pin at the back of thecrankcase opening (1001). Do notinstall the cooling head until these twoitems are keyed into each other.

Place the copper head gasket onto thesleeve and fit the cooling head into the sleeve (1002). Note that there aretwo slots notched through the cooling fins on each side of the cylinderhead.These slots are for access to the engine mounting screws.The fivehead bolts should line up with the five holes on top of the engine caseand the access slots on the cooling head should line up with the slotsmanufactured into the crankcase. Be careful not to damage the copperhead gasket (see picture 1002 for orientation).

While pressing the head squarely onto the sleeve, thread the head boltsinto the engine case just until they stop. Do not tighten down these boltsindividually. It is very important to attain even pressure around the coolinghead. Slowly tighten each screw, just a little at a time, in a crossing pattern(see picture 1003) until each bolt becomes snug. Finish each bolt in thesame pattern with 9-11in•lbs. of torque.

37


9. Apply a drop of after-run oil in thepiston’s wrist pin bore, before installingthe wrist pin. Locate the oiler hole (referto pic 901) in the connecting rod and theskirt relief side of the new piston.

Insert the connecting rod into the pistonwith the piston skirt relief and the oilerhole on the same side (901). Line up thewrist pin bore in the rod with the wristpin bore in the piston and slide the wristpin through the larger opening in thepiston. Note that the closed end of thewrist pin should be inserted first into theopening.The orientation of the wrist pinhelps keep the wrist pin cool.

Install the wrist pin clip into the grooveof the piston’s wrist pin bore (902).Thiswill retain the wrist pin inside of thepiston . Caution: Do not allow the pliersto scratch the piston, and make surethat the clip expands into the groovebefore moving on.

Lower the piston and connecting rodassembly into the top of the engine casewith the oiler hole of the connecting rodfacing toward the crankshaft. Apply adrop of oil onto the crank pin beforeinstalling the connecting rod onto thecrank pin. Slide the connecting rod overthe crank pin and rotate the crank pin tothe bottom center of the crankcase (903).

901

902

903

1001

1002

1003

Skirt Relief OilerHole

11. Inspect the backplate bushing andstarter shaft for wear and clean themwith denatured alcohol. Fasten thebackplate with the starter shaft to thecrankcase. Important: The reliefs thatare manufactured into the backplatemust line up to match the ports insideof the engine case (see picture 1101for orientation).

Key the starter shaft to the crank pinby slowly rotating the starter shaft as pressure is applied towards thecrankshaft. Once the starter shaft iskeyed into the crank pin, join thebackplate to the engine case andsecure the assembly with the four3x6CS screws (1102). (On non-startermodels simply fasten the backplate tothe crankcase with (4) 3x6BCS screws).

Install a new glow plug (Traxxas #3231is recommended for the TRX 2.5) intothe cooling head.The engine is nowrebuilt and ready for the installation of the clutch assembly and the EZ-Start 2 system (if so equipped).

12. Slide the split cone washer over thepilot shaft with the larger end of thetaper toward the engine case (1201).Slide the flywheel over the pilot shaftand onto the split cone washer.

The split cone washer should fit inside of the tapered hole in the flywheel.Thread the flywheel nut all the way upto the flywheel and tighten the flywheelwith 55-65 in•lbs. of torque against theflywheel (1202).

13. Slide the clutch shoes onto theflywheel. Key the flywheel pins into theholes of the clutch shoes (See picture1301 for orientation of the clutch shoes).

Tip: By reversing the direction of theclutch shoes, the clutch shoes willprovide a little firmer bite against theinterior wall of the clutch bell.This isuseful on higher bite surfaces that offera higher level of traction.

14. Clean and lube both clutch bellbearings and install a ball bearing intoeach side the clutch bell and slide theclutch bell over the pilot shaft followedby the 5x8x0.5TW (1401).

Fasten the 5.0 E-clip (wearing safetyglasses) around the pilot shaft to retainthe clutch assembly.

Note: The Nitro 4-Tec will need two5x8x0.5TW slid onto the pilot shaftbefore the installation of the clutch bell, then secure the assembly with the 3x10CS screw.

1201

1202

1203

1301

1401

1102

38


1101

39


15. Clean the roller clutch with denaturedalcohol or electric motor spray, and lubethe roller clutch with after-run oil. Slidethe roller clutch onto the starter shaft asshown (1501).

Note: The roller clutch is to be installedonto the starter shaft so that the clutchengages the starter shaft clockwise androtates freely counter-clockwise.Theengraved text on the roller clutch facesthe engine backplate for correct rotation.

Slide the EZ-Start 2 system or pull startonto the starter shaft that exits thebackplate of the engine. Line up the drivewith the roller clutch. Fasten the EZ-Start 2gear case to the backplate with the three3x12BCS screws (1502). Fasten the pullstarter with (4) 3x12BCS.

16. Inspect the exhaust o-ring and replaceit if it is damaged or torn. Fasten theexhaust header and pipe assembly backonto the rear of the engine case with thetwo 3x15CS screws (1601).

The engine, clutch, exhaust system and starter assembly is now readyfor installation into the chassis (1602).

Follow the proper break-in procedure perinstructions for the new TRX 2.5 engine.

1501

1502

1602

1601

TRX 2.5 Racing EngineOwner’s Manual

Covers Models 5204,

5206, 5207, 5209Traxxas Corporation, 1100 Klein Road, Plano, Texas 75074, Phone: 972-265-8000, Toll-free 1-888-TRAXXAS

Traxxas U.K., P.O. Box 1128, Winterbourne, Bristol BS17-2SH, England, Phone: 44-117-956-1002Internet: www.Traxxas.com, www.ReadyToRun.org

TRX 2.5 Racing Engine - Blade - #1 By Design

Documents

Transcript of TRX 2.5 Racing Engine - Blade - #1 By Design