Dr. Felix Wankel's rotary four-stroke engine of the fifties separated the induction, compression, ignition and exhaust phases through three individual chambers with a triangular rotor taking the place of pistons.
Advantages are that it's a fairly compact design, with fewer moving parts than a regular piston-equipped engine, and the power is much smoother. Set against that is the fact that these engines are not particularly fuel-efficient or emissions-friendly. Suzuki got the ball rolling with the RE5, back in 1975, but Norton is perhaps the most famous rotary manufacturer. From their earlier association as an amalgamation of European manufacturers, they had the license to build a Wankel motorcycle.
This eventually became successful in British motorcycle racing in the eighties and nineties. Brian Crighton was the man behind turning the police bikes into race bikes, transforming a 70 horsepower turned into a 135 horses missile.
The JPS Nortons and the Roton twin-shock race bikes were a pleasure to see on the racetracks, even if they were about as legal as smoking at a public place in Thailand. The Norton F1 looked nothing like the bike that was being raced. The Norton 1990 F1 cost around 850,000 Baht (what is about 25,500 USD), fuel consumption best compared to big American V8 Chevrolet's from the 70s and was about as 'clean' as my garage after I slipped some old engine oil cans. Then there was the question of capacity.
Some measured the bike at 588cc while others doubled it to 1176cc. Less reciprocating weight also meant little engine braking, making Mallory Park's hairpin a good place to watch the novice Norton pilot.