The battery supplies the power necessary to start the engine when the ignition switch is is turned on.

During the exhaust stroke, just before the piston reaches bottom dead center the exhaust valve opens. The resulting gases from combustion are then pushed out through the exhaust valve as the piston travels up the cylinder to top dead center, completing stroke four of the four-stroke piston cycle.

Ignition timing defines the point in time at the end of the compression stroke that the spark plug fires. Measured in number of degrees before top dead center (BTDC), the exact point that the spark plugs initiate combustion varies depending on the speed of the engine. The timing is advanced (the spark plugs fire a few more degrees BTDC) when the engine is running faster and retarded when it's running slower.

The intake manifold distributes outside air to the intake ports on the cylinder heads. The intake air filter removes any airborne contaminants before the air enters the engine.

Spark plugs receive current from the distributor and use it to spark combustion in the combustion chamber of a cylinder.