Wankel rotary engine
A rotary engine using a triangular rotor creates three chambers, each performing the same cycles as a four-stroke engine.
Rotary engines are a motorcycle curiosity and worth mentioning. Rotary engines have been around since the dawn of the piston engine. It was not until 1954, when Felix Wankle developed his breakthrough rotary that the design became more than a curiosity. During the 1970s world oil crises, great interest was paid to the Wankel rotary engine. BSA, Norton-Villiers-Triumph, Hercules and Suzuki produced production motorcycles with the engine. Yamaha developed the RZ201 concept but never pushed it into production. Suzuki, Norton, Van-Veen and Hercules are the only two motorcycle manufacturers to put the engine into production. (The 497cc Suzuki wankle produced 62 horsepower and was capable of 115 m.p.h.)
Rotary engines achieve compression by rotating a convex triangle concentrically in an oblong chamber. At various points along its path the triangle creates compression between itself and the chamber.
Rotaries have fewer parts and weigh less than piston engines of equivalent power. They are quiet, produce very little vibration and offer an extremely sweet power curve. But the Wankel has not enjoyed the success of the piston engine for several reasons. Probably the most significant reason is that the piston engine is simple, abundant and understood.