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The Epic Interactive Encyclopedia 1997
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1992-09-02
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21 lines
Operating cycle for internal combustion
piston engines. The engine cycle is completed
after just two strokes (movement up or down)
of the piston, which distinguishes it from
the more common four-stroke cycle. All
lightweight motorbikes use two-stroke petrol
engines, which are cheaper and simpler than
four-strokes. Most marine diesel engines are
also two-strokes. In a typical two-stroke
motorbike engine, fuel mixture is drawn into
the crankcase as the piston moves up on its
first stroke to compress the mixture above
it. Then the compressed mixture is ignited
and hot gases are produced, which drive the
piston down on its second stroke. As it moves
down, it uncovers an opening (port) that
allows the fresh fuel mixture in the
crankcase to flow into the combustion space
above the piston. At the same time the
exhaust gases leave through another port.