BMW R51/3

The BMW R51/3 was BMW's second post-World War II 500 cc motorcycle, following the briefly produced R51/2, and it featured a flat-twin engine and an exposed drive shaft. In 1951 it succeeded and modernised the 1950 R51/2, which was essentially a pre-war design built after the war, and it stayed in production for four years. After the war the Allies had barred Germany from making motorcycles, and when the ban was lifted in Western Germany BMW had to start from scratch with no plans or blueprints, using surviving pre-war motorcycles to draw new ones; the first postwar machine was the 250 cc R24 of 1948, essentially a pre-war R23 with a rigid rear end. The 600 cc R67 series, a near identical sister model, and the more sporting R68 followed alongside it.