BMW 1939 R51RS 494 cc OHV transverse twin engine # 505758, frame # to be advised
This machine is one of the 20 genuine production racers which BMW completed and sold in 1939. In order to cash in on the successes of the Kompressor-BMWs (superchargers) of mainly Ernst Henne and Georg “Schorsch” Meier from 1936 till 1939, BMW also strived to offer a production racer which could match the English single cylinders on the circuits of Europe.
In 1937 an experimental model was built with which Schorsch Meier competed in the very tough ISDT of 1937.
However, it took till the winter of 1938/1939 for BMWs race department to start the production of a batch of 20 engines.
Due to the beginning of WWII only 17 machines were completed and sold; surprisingly some 4 years ago number 18 emerged in the USA in a very original state.
The R51RS was based on the standard R51 (1938-1940).
The racing department had produced a lot of special parts: the R51’s chain for driving the camshaft was replaced by a train of skew gears, the dynamo and the battery-ignition was replaced by a Bosch racing magneto as used on the Kompressor-BMW and almost all engine covers were replaced by identical parts cast in magnesium.
The RS was fitted with 21 “ front wheel and 20”rear wheel just as the K-models had been.
The heart of this particular RS is the second engine that has been manufactured/ delivered . The complete engine housing, the magneto and the camshaft drive are original; over the years all of the rest has been improved/replaced by newer parts in order to make the engine perform better as a sidecar-outfit on the post-war circuits in Germany.
At present there are a lot of replicas around, which mainly are based on Ernst Hoske’s replica of the R51RS.
This however is quite distinguishable from the original BMW-design.
All in all this exciting racing machine can be brought back to its original condition without encountering big problems.