Two-stroke engine

The two-stroke engine is an internal combustion engine. The two strokes are:

Stroke	Number	Piston	Intake port	Exhaust port
		bottom dead center	open	open
compression	1	piston rising	closed	closed
		top dead center	closed	closed
firing	2	piston descending	closed	closed

Animation of two-stroke engine

Unlike a four-stroke engine, there are no intake and exhaust strokes. When the piston is at bottom dead center, fuel-air mixture is blown in under slight pressure. The incoming mixture forces out the exhaust gas at the same time. The animation shows an engine with crankcase compression to force in the fuel-air mixture. Some engines use a rotary blower instead. These engines use mixed fuel (often 50:1) primarily high octane gasoline, partially two-stroke oil.