SMALL GAS ENGINESAg Science and Tech

OBJECTIVES

Understand correct safety procedures when working with small gas engines in the shop.

Identify tools used when working with small gas engines.

Describe the strokes of 2-stroke and 4-stroke engines.

Define the components of a small gas engine and their functions.

TERMS

Engine Internal combustion

engine Piston Piston rings Connecting rod Crankshaft Crankcase Valves

Intake valve Exhaust valve Valve lifters Cylinder head Camshaft Carburetor Flywheel Spark plug

FUNCTION OF ENGINES

Engine A device for converting chemical

energy into mechanical energy. Internal combustion engine

Device that burns fuel inside a cylinder to create a force that drives a piston.

SAFETY

Safety glasses must be worn at all times.

Keep hands and feet away from all moving parts during operation.

Keep all ignition sources away from the work area.

Stop engine and allow it to cool before refueling.

Handle gasoline outdoors if possible.

Disconnect the spark plug lead when making adjustment to prevent accidental start-up.

Never disengage any of the safety equipment or devices.

SAFETY

Keep all shields in place.

Do not operate engines above the specified speed.

Never overload engines or force equipment beyond it the designed capacity.

Never use gasoline as a solvent to clean parts.

Only start and run engines where ventilation is adequate, preferably outdoors.

Never pour gasoline or oil on the ground or down a drain, dispose of it in the correct container to be recycled.

ENGINE COMPONENTS

Piston Crankshaft Crankcase Valves Camshaft Cylinder Cylinder head Carburetor Flywheel Spark plug

PISTON

Located in the cylinder Piston rings- an expanding ring

placed in the grooves of the piston to seal it against the passage of fluid or gas.

CONNECTING ROD

Piston is connected to the crankshaft by the connecting rod.

CRANKSHAFT

Converts up and down motion into rotating force.

CRANKCASE

Holds the crankshaft in place. Also houses the camshaft and oil.

VALVES

Intake valve Allows air/fuel mixture to enter the

combustion chamber. Exhaust valve

Allows fumes to exit the cylinder. Valve lifters

Moves the valves up and down Powered by the camshaft

CAMSHAFT

Operates opening and closing of the valves.

Rotated by a gear on the crankshaft.

CYLINDER

Combustion chamber Where the piston is located Cylinder head- seals the cylinder

CARBURETOR

Mixes air and fuel before it is pulled into the combustion chamber.

FLYWHEEL

Turned by crankshaft to induce electrical current with magnet through the magneto.

Momentum

SPARK PLUG

Supplies spark.

2-STROKE ENGINES

Combustion Compression

4-STROKE ENGINES

Intake Compression Power Exhaust

CLASSIFYING ENGINES

2- or 4-stroke Amount of power they produce

<25 hp = small engine >25 hp = large engine

Number of cylinders Single-cylinder Multi-cylinder

CLASSIFYING ENGINES

Engine displacement Total swept volume of the engine cylinders

as the piston completes one stroke. Cylinder arrangement

In-line Vee-block

Fuel Gasoline Diesel

MICROMETER

INSIDE MICROMETER

FEELER GAUGES

SPARK PLUG GAP

TORQUE WRENCH

COMPRESSION GAUGE

TELESCOPING GAUGE