Types
Almost all production motorcycles have gasoline (UK petrol) internal combustion engines. Both four-stroke and two-stroke engines are used, but strict emission laws have led to far fewer two-strokes. A few have used Wankel rotary engines, but no Wankel bikes are currently in production. Motorcycle engines can be air cooled or liquid cooled, and optionally include oil cooling as well. Some scooters use batteries and an electric motor. (The 2009 TT races introduced a new category 'TTX' for electric bikes using fuel-cells or batteries).
Motorcycle engines can be mounted transversely; with the crankshaft aligned perpendicular to the frame or longitudinally, with the crankshaft parallel to the frame. Motorcycles with transversely mounted engines are more suited to have chain or belt final-drive. Motorcycles with longitudinally mounted engines are more suited for shaft final-drive.
Motor scooters have the engine as part of the rear suspension, so the engine not fixed rigidly to the main frame. Instead, the combined engine-transmission-swingarm assembly is pivoted to follow the road surface and is part of the "unsprung weight". The chain final-drive of scooters runs in an oil-bath within the engine casings. "Step-throughs" motorcycles may have a rigidly fixed engine, or may have a scooter-type arrangement.
Read more about this topic: Motorcycle Engine
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