Engine displacement is a measurement of the amount of space displaced by the movement of a piston. It is traditionally used to differentiate between classes of motorcycles but isn't always indicative of performance. Two stroke motorcycles often are able to have quite lower engine displacements and reach the same level of performance of comparable four stroke.
Displacement = radius squared x 3.14 x stroke x number of cylinders.
Also see: cc (cubic centimeters)
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