BMW's motorcycle history began in 1921 when the company commenced manufacturing engines for other companies. Motorcycle manufacturing now operates under the BMW Motorrad brand. BMW (Bayerische Motoren Werke AG) introduced the first motorcycle under its name, the R32, in 1923.
BMW merged with Bayerische Flugzeugwerke in 1922, inheriting from them the Helios motorcycle and a small two-stroke motorized bicycle called the Flink. In 1923, BMW's first "across the frame" version of the boxer engine was designed by Friz. The R32 had a 486 cc (29.7 cubic inches) engine with 8.5 hp (6.3 kW) and a top speed of 95 to 100 km/h (59 to 62 mph). The engine and gearbox formed a bolt-up single unit. At a time when many motorcycle manufacturers used total-loss oiling systems, the new BMW engine featured a recirculating wet sump oiling system with a drip feed to roller bearings. This system was used by BMW until 1969, when they adopted the "high-pressure oil" system based on shell bearings and tight clearances, still in use today.
The R32 became the foundation for all future boxer-powered BMW motorcycles. BMW oriented the boxer engine with the cylinder heads projecting out on each side for cooling as did the earlier British ABC. Other motorcycle manufacturers, including Douglas and Harley-Davidson, aligned the cylinders with the frame, one cylinder facing towards the front wheel and the other towards the back wheel. The R32 also incorporated shaft drive. BMW has continued to use shaft drive on its motorcycles and did not produce a chain driven model until the introduction of the F650 in 1994.
In 1931, BMW introduced the single-cylinder shaft-driven R2, which, as a 200 cc motorcycle, could be operated in Germany without a motorcycle licence at that time. The R2 headed a series of single-cylinder BMW motorcycles, including the 400 cc R4 in 1932 and the 300 cc R3 in 1936.
The BMW R12 and R17, both introduced in 1935, were the first production motorcycles with hydraulically damped telescopic forks.
In 1937, Ernst Henne rode a supercharged 500 cc (31 cubic inches) overhead camshaft BMW 173.88 mph (279.83 km/h), setting a world record that stood for 14 years.
Construction was so good that during World War II Harley-Davidson copied the BMW engine and transmission—simply converting metric measurements to inches—and produced the shaft-drive 750 cc (46 cubic inches) 1942 Harley-Davidson XA.
The terms of Germany's surrender forbade BMW from manufacturing motorcycles. In 1946, when BMW received permission to restart motorcycle production from US authorities in Bavaria, BMW had to start from scratch.
In 1955, BMW began introducing a new range of motorcycles with Earles forks and enclosed drive shafts. These were the 26 hp (19 kW) 500 cc R50, the 30 hp (22 kW) 600 cc R60, and the 35 hp (26 kW) sporting 600 cc R69.
On June 8, 1959, John Penton rode a BMW R69 from New York to Los Angeles in 53 hours and 11 minutes, slashing over 24 hours from the previous record of 77 hours and 53 minutes set by Earl Robinson on a 45 cubic inch (740 cc) Harley-Davidson.
For the 1968 and 1969 model years only, BMW exported into the United States three "US" models. These were the R50US, the R60US, and the R69US. On these motorcycles, there were no sidecar lugs attached to the frame and the front forks were telescopic forks, which were later used worldwide on the slash-5 series of 1970 through 1973. Earles-fork models were sold simultaneously in the United States as buyers had their choice of front suspensions.
In 1970, BMW introduced an entirely revamped product line of 500 cc, 600 cc and 750 cc displacement models, the R50/5, R60/5 and R75/5 respectively and came with the "US" telescopic forks noted above. The engines were a complete redesign. The roller and ball-bearings in the bottom end had been replaced by shell-type journal bearings similar to those used in modern car engines. The camshaft, which had been at the top of the engine, was placed under the crankshaft, giving better ground clearance under the cylinders while retaining the low centre of gravity of the flat-twin layout. The new engine had an electric starter, although the traditional gearbox-mounted kick starter was retained. The styling of the first models included chrome-plated side panels and a restyled tank. The /5 series was given a longer rear swingarm, resulting in a longer wheelbase. This improved the handling and allowed a larger battery to be installed.
The /5 models were short-lived, however, being replaced by another new product line in 1974. In that year the 500 cc model was deleted from the lineup and an even bigger 900 cc model was introduced, along with improvements to the electrical system and frame geometry. These models were the R60/6, R75/6 and the R90/6. In 1973 a supersport model, the BMW R90S, was introduced. In 1975, the kick starter was finally eliminated.
In 1995, BMW ceased production of airhead 2-valve engines and moved its boxer-engined line completely over to the 4-valve oilhead system first introduced in 1993.