BMW R 6

The BMW R 6 was BMW's first motorcycle in the 600 cubic centimetre class, introduced in February 1937 at the Berlin motor show, a year after the sporting R 5. It paired a new side-valve boxer twin, built with a tunnel crankcase and a long 78 millimetre stroke, with the gearbox and frame of the R 5, so one manual and parts list served both bikes. Two Amal carburettors and a shared air filter on the gearbox housing fed the engine, and the Bosch battery ignition was adjusted by a lever on the left handlebar. A four-speed foot-shifted gearbox drove the rear wheel by shaft, the welded double-loop frame had no rear suspension, and an oil-damped telescopic fork guided the front wheel. It sold for 1,375 Reichsmark, 255 less than the 750 cubic centimetre R 12, and 1,850 were built in 1937. The R 61 with plunger rear suspension followed in 1938.