1976 Suzuki RE5 Rotary
In theory, a rotary engine is a study in simplicity. There are no camshafts, no intake or exhaust valves, and considerably fewer moving parts than you’ll find in a piston engine.
All that made the rotary design, also known as the Wankel engine, an attractive alternative to piston power in the early ’70s.
In practice, though, at least as far as Suzuki was concerned, building a rotary-powered motorcycle turned into an incredibly complex engineering exercise. This 1976 Suzuki RE5, donated to the Motorcycle Hall of Fame Museum located at AMA headquarters in Pickerington, Ohio, by Patrick Brewer of Cincinnati, shows why.
Simply lubricating the engine required technology never before used on a motorcycle. The RE5 had a traditional wet-sump oil system similar to those on four-stroke piston engines. But to adequately lubricate the rotary’s four-piece seals — the equivalent of rings on a piston engine — a secondary oil system was needed. The supply tank for it resides under the seat and feeds oil into the float bowl of the carburetor, much like injector systems on two-stroke engines.
The carburetor itself looks like it would be more at home under the hood of a Ford. It is a two-barrel, down-draft, 18-32mm automotive-style carb weighing five pounds. No less than five cables and an assortment of linkages sprout from the device.
The ignition system also broke new ground in terms of complexity. The RE5 actually has two -- one to deliver spark under normal riding conditions, and another offering altered ignition timing under deceleration above 1,700 rpm. Without the second system, the rotary had an annoying habit of popping, bucking and sometimes accelerating when the throttle was shut off.
Even the exhaust system had to be re-engineered. Rotary engines dump a lot of heat into the exhaust pipe, which wasn’t a problem for Wankel-engine cars. But on a motorcycle, that heat is literally inches from the rider’s legs. So Suzuki designed a way to duct air into the exhaust system to help keep the temperature under control.
To Suzuki’s credit, the high-tech RE5 worked fairly well. But all that complexity resulted in a hefty curb weight of 573 pounds. That bulk, coupled with the rotary’s large appetite for fuel, resulted in gas mileage in the 30 to 35 mile-per-gallon range at a time when Americans were facing gas crises. And the bike’s limited cruising range didn’t endear it to the touring market it was designed for.
In short, Suzuki had built an interesting answer to a question no one had asked.
It may be this novelty, though, that has made the RE5, built only from 1975 through ’77, one of the most memorable and collectible bikes of the ’70s.