1938 BMW 500cc R51RS Racing Motorcycle

• Rare factory-built pre-war BMW racer
• Reportedly raced by Otto Kolle
• Raced in the UK by John Joiner
• Present ownership since the late 1980s

This BMW R51RS is one of 17 overhead-valve factory racers produced as 'practice' machines. Some went to dealers who supported riders. It is even rarer that the Rennsport, of which there were around 24 RS53 and RS54 made. This machine was raced successfully with a sidecar attached, by Otto Kolle and later John Joiner. It has the distinction of being the first non-British motorcycle to win a VMCC race. This was at Mallory Park with John Joiner (still with the sidecar attached). The BMW started at the back of the grid but emerged from Gerard's in the lead on the last lap.

In more recent time the bike has been rebuilt as a solo racer, more like it would have left the factory.
The machine now has a replacement frame, '505657', acquired from the late Dave Dickinson of Tintern Garage. The engine currently fitted has no number.

Engine differences between the R51 and the R51RS are the latter's aluminium barrels with cast-iron liners, and six turnbuckles with a coarse thread on one and and a fine on the other, enabling the barrels to be clamped between the crankcase and cylinder head when tightened. Pistons were special Mahle high compression. Twin Bing carburettors were later replaced with twin Amal TTs with special induction stubs. Chain driven camshafts now replaced with gears; only the magneto is chain driven.

John Joiner first came across this BMW at Cadell Park in 1975, where he was racing a Triumph Tiger 100 outfit. Joiner acquired the Beemer in a part-exchange deal with fellow sidecar competitor, the late Dave Treen. John Joiner later discovered that the BMW had been raced by Otto Kolle and fitted with a works-prepared R51RS Type 254(RS) engine. When purchased from Dave Treen the outfit was complete with a Watsonian racing sidecar platform. In 1976 John took the outfit to a Silverstone practice session and found that the engine would rev freely to 10,000rpm.

The BMW's subsequent history is not known prior to the vendor acquiring it from Trevor Hopkinson in the late 1980s. The engine was then stripped and rebuilt, the carburetion sorted, and any other niggling issues addressed. According to the vendor, the machine runs quite well but still needs a bit more 'tweaking'. A fuller account of the BMW's history may be found within the accompanying file.
Key not required