A two-stroke (or two-cycle) engine is a type of internal combustion engine which completes a power cycle with two strokes (up and down movements) of the piston during only one crankshaft revolution. This is in contrast to a "four-stroke engine", which requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. read more
2) Power. 3) Exhaust. 4) Intake. A two-stroke engine performs all the same steps, but in just two piston strokes. The simplest two-stroke engines do this by using the crankcase and the underside of the moving piston as a fresh charge pump. Such engines carry the official name “crankcase-scavenged two-strokes.” As the two-stroke’s piston rises on compression, its underside pulls a partial vacuum in the crankcase. read more
The following animation shows a two-stroke engine in action. You can compare this animation to the animations in the car engine and diesel engine articles to see the differences. read more