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A two-stroke engine

A two-stroke engine Cylinder head Carburettor Supplies fuel/air/oil mixture to engine. Lubricating oil can be fed separately instead. Inlet ports Lead to the crankcase, where initial compression takes place. Bearings Ball or needle roller types are used as they can run in an oil mist. Crankshaft Transfer ports Lead the intake mixture from the crankcase to the top of the cylinder after crankcase compression. Water cooling jacket Pistons Sometimes have cut-outs to let the inlet charge through. They can be shaped on top to control inlet and exhaust flow. Exhaust Ports and pipe must be accurately designed to help control the flow of exhaust and inlet gases.

Most two-stroke engines are of the crankcase compression type. The fuel/ air mixture is fed into the crankcase through the side of the piston from an inlet manifold mounted low down on the cylinder. The mixture is slightly compressed in the crankcase then transferred to the top of the cylinders, compressed and ignited so that the burning gases expand to drive the pistons down.

Lubricating oil is mixed with the fuel or injected separately. Because the crankshaft bearings are not pressure-fed with oil, they are of the ball or needle-roller bearing type which can operate in an oil mist.