The four stroke engine is an internal or heat combustion engine commonly used to power transport vehicles. The complete cycle requires four successive phases. During the intake stroke, a fuel-air mixture is drawn into the cylinder. It is then compressed by the upward movement of a piston. The mixture is ignited by a spark plug to initiate the combustion stroke, the source of power, and finally the spent gases are forced out during the exhaust stroke. The cycle repeats itself over and over again.
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