BMW 247 engine

The BMW 247 engine is an air-cooled flat twin motorcycle engine with two valves per cylinder, also known as the "airhead" boxer. It was used by BMW in its motorcycles from 1969 to 1995.

The /5 variant was introduced in 1969, /6 in 1974 and the /7 in 1977. Before 1981 the ignition was points ignition. From 1981 it used electronic ignition, a lighter flywheel and was slower.

A number of different models were on the market:
*CS: the Classic Sport, with a 1000 cc engine.
*GS: Gelände/Strasse - winner of a number of the Dakar rallies.
*RS: Renn (Racing) Sport
*RT: Road Touring
*S: with the most famous BMW R 90 S, which was as fast as the Porsche Boxster in acceleration.
*ST: An 800 cc road-styled G/S.

Prior to the type 247, BMW also built other air-cooled flat twin engines known as the Typ 248/1 used for the R45, the R65 and the R65LS BMW motorcycles. Before that they built side-valve and OHV engines commencing with the R32 of 1923. After the type 247, BMW substanitally changed the engine design to include partial oil cooling and four valves per cylinder, a design which was to become known as the "oilhead".