Since the Allies had restricted German manufacturers to production of motorcycles below a capacity of 250 cc, development plans for a large BMW Boxer motorcycle were initially set to one side. In 1950, production of the BMW R 51/2 started up, which was based on the prewar BMW R 51 and had taken over the chassis and basic design of the engine. The main optical difference was provided by the split valve covers held together with a clip. The BMW R 51/2 demonstrated that BMW was in tune with the times and 5,000 units were manufactured in a production run lasting one year.