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Wheels on Reels

Classic motorcycle videos selected by the editors of Motorcycle Classics

The Theory Behind the Suzuki RE-5 Rotary Motorcycle

rotary engine 
An illustration of the rotary engine's operation. 

Although effectively simple in design, describing the engine on a rotary motorcycle is not easy, and Suzuki went to great pains in its own advertising material to educate motorcyclists on the theory of its new engine for the Suzuki RE-5.

Unlike a conventional four-stroke where a piston travels up and down through two complete crankshaft revolutions to complete one full power cycle of four strokes — intake, compression, ignition and exhaust — a three-sided rotary engine completes one power cycle for every revolution of its output shaft. For this to occur, a tri-tipped rotor rotates inside what looks like an oblong housing. The rotor’s tips seal against the housing to form combustion chambers. Instead of a crankshaft, a rotary uses an eccentric shaft with the rotor riding on the eccentric. A stationary gear on the end of the eccentric shaft keys the rotor to the eccentric shaft. Combustion pressure pushes the rotor away from the combustion face, causing the eccentric shaft to rotate. The shaft’s eccentric defines the throw of the rotor while the stationary gear defines the rotor’s position on its axis. As the rotor spins, its axis shifts, causing the rotor to orbit and alter the combustion chamber for intake, compression, ignition and exhaust phases. Think planetary motion and you’ll get the basic idea. Here's a fascinating two-part video on the story behind the Suzuki RE-5: