two-stroke engine

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two-stroke engine Internal combustion engine in which the operation of each piston is in two stages. In the two-stroke cycle, a piston moves up a cylinder to compress a fuel-air mixture in the top. At the same time, more of the mixture is sucked in below the piston. A spark ignites the compressed mixture, causing an explosion. This sends the piston back down the cylinder. The piston forces the fresh fuel-air mixture out from beneath it, and along a transfer port leading to the top part of the cylinder. The mixture forces the exhaust gases out from the top of the cylinder. The process then repeats. See also four-stroke engine