BMW Airhead Boxer Twin Engine (1923–1995)

The BMW Airhead is one of the most storied engine architectures in motorcycling — a longitudinally-mounted air-cooled OHV 2-cylinder "boxer" (horizontally opposed) that has been refined continuously since Max Friz designed the original R32 in 1923. The R32, R69S, R90S, and R100RS all share the same 90° crankshaft phasing, shaft drive, and cross-head pushrods — evolution within an unbroken design lineage spanning seven decades. The R90S of 1973 was the fastest production motorcycle in the world. The R100RS of 1976 pioneered full-fairing aerodynamics on a production motorcycle.