BMW 247 engine

1994 BMW R100RT with type 247 engine
1973½ BMW R75/5 with type 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 (MY 1970) introduced first modern BMW boxer engine; the BMW 246 engine of the /5 series. With minor and more significant updates (247/76 in 1976 and 247/M80 in 1981) 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.[1]

A number of different models were on the market:

  • CS: the Classic Sport, with a 1,000 cc (61 cubic inches) engine.
  • GS: Gelände/Straße - winner of a number of the Dakar rallies.
  • RS: Renn (Racing) Sport
  • RT: Road Touring
  • S: with the R90S
  • ST: [Straße]. An 800 cc (49 cubic inches) road-styled G/S.

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".

References

  1. ^ Falloon, Ian (November 2003). The BMW story: production and racing motorcycles from 1923 to the present day. Sparkford, England: Haynes Publishing. p. 85. ISBN 978-1-85960-854-8.


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