In 1938 BMW introduced the R-71. It was a 750 cc flat twin motorcyle which had plunger rear suspension. It was intended as a touring bike, and to pull a sidecar. At that time the German Army was not interested in going to a new design and choose to stay with the proven R-12. They did put out a contract with both BMW and Zundapp to produce a military motorcycle. These were to become the R-75 and KS-750. The Soviet military was looking for a new motorcycle at this time and contraced with BMW to build the R-71 under license. This became the M-72 later called the Ural and Dnepr. After the war the Soviets sold the machinery to the Chinese. Over the years the Soviet designs evolved, typicly a few year after BMW changed their designs. The Chinese however did little or no modification. So esentually you can still buy a new 1938 BMW R-71. Only it is made by the Chinese and called the Chiang Jiang 750.
This is an original of the German R-71. This is Dave Thorp's (of Motorcycle Online) 1937 R-12.