FOUR (4) STROKE CYCLE ENGINES. A four-stroke cycle engine is an internal combustion engine that completes one cycle through four piston strokes: intake, compression, power, and exhaust, requiring two crankshaft revolutions (720°). This type of engine is common in small applications. Intake Stroke-The piston moves down, creating low pressure that allows the air-fuel mixture to enter the combustion chamber through the open intake valve, which closes after the cylinder fills. Compression Stroke- Th