The motorcycle power unit uses the internal combustion engine; People are accustomed to using diesel as fuel engines called diesel engines, and the use of gasoline as fuel engines called gasoline engines. Because gasoline engine has the advantages of light weight, small volume, low noise, low vibration, easy starting and low cost, so the motorcycle generally uses gasoline engine as its power device. Two-stroke engine: where the engine crankshaft rotates once, that is, the piston moves two strokes up and down to complete a working cycle of the engine. Four-stroke engine: where the engine crankshaft rotates twice, that is, the piston moves up and down four strokes to complete a working cycle of the engine. The working cycle refers to the working process of the engine composed of intake air, compression, combustion expansion (work) and exhaust stroke. The process of the engine completing an intake, compression, work and exhaust is called a working cycle, also known as a cycle.