BMW 247 engine

The BMW 247 engine is an air-cooled flat-twin motorcycle engine with two valves per cylinder, also known as "airhead" boxer. The 247 engine was the successor of the in 1969 introduced first modern BMW boxer engine; the BMW 246 engine of the /5 series. With minor and more significant updates it was used by BMW beginning with the 1974 /6 series in its motorcycles from 1974 to 1995.
Before 1981 the ignition was points ignition. From 1981, introduced in the R80G/S it used electronic ignition, Nikasil cylinders, and a lighter flywheel.
A number of different models were on the market:

Subsequent to the type 247 motor, 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 substantially changed the engine design to include partial oil cooling and four valves per cylinder, a design which was to become known as the "oilhead".