Two-Stroke Engine

A two-stroke engine, or two-stroke cycle engine, is a type of internal combustion engine that completes a power cycle with two strokes of the piston, one up and one down, in a single revolution of the crankshaft, in contrast to a four-stroke engine, which requires four piston strokes over two crankshaft revolutions to complete a power cycle. Two-stroke engines often have a higher power-to-weight ratio than four-stroke engines, since their power stroke occurs twice as often, and can also have fewer moving parts, making them cheaper to manufacture and lighter in weight. In regions with stringent emissions regulation, two-stroke engines have been largely phased out of automotive and motorcycle use, though small-displacement two-stroke engines remain popular in mopeds and motorcycles elsewhere, and in power tools such as chainsaws and leaf blowers.