A prewar package of beauty, economy and efficiency
BMW launched ITS first motorcycle in 1923, the shaft-driven R32 494cc sidevalve flat twin, the basis of the now instantly recognisable Boxer engine. The company’s solid, reliable twins have certainly stood the test of time, with a plethora of models and variants in different guises, but BMW’s lesser known singles are equally intriguing and well worth investigating.
BMW’s first single cylinder machine, the 250cc R39, was launched in 1925, two years after the R32. This was followed by the 200cc R2 from 1931 to 1936, the 400cc R4 from 1932 to 1937 and the 1936 300cc R3 singles. Interestingly it was to be 70 years before BMW offered a chain driven option, and the 1993 Rotax-engined F650 was a significant change from BMW’s standard powerplants.
The R4 was replaced in 1937 by the R35. Using the R4 engine as a basis, the bore was reduced to bring capacity down to 340cc; the cylinder head was taken from the less commercially successful R3. In common with its predecessors the R35 has a pressed steel frame, the last BMW single to do so. Other BMW models at the time had twin loop tubular frames, however, the R35 was a budget model so the pressed steel frame kept costs down, as did the telescopic forks with no hydraulic damping. Even without damping the telescopic forks were a vast improvement over the R4’s forks which had a basic cantilever spring, friction dampers only being fitted to late R4 models.
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