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