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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 to 1925.

BMW began in 1916 as a reorganization of Rapp Motorenwerke, an aircraft engine manufacturer that began production before World War I. With the Armistice, the Treaty of Versailles banned the German air force and the manufacture of aircraft in Germany, so the company turned to making air brakes, industrial engines, agricultural machinery, toolboxes and office furniture and then to motorcycles and cars.

In 1921, BMW began manufacture of its M2B15 flat-twin engine. Designed by Max Friz for use as a portable industrial engine, the M2B15 was largely used by motorcycle manufacturers, notably Victoria of Nuremberg, and Bayerische Flugzeugwerke in their Helios motorcycle. Friz was also working on car engines.

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 in line crank with two horizontally opposed air cooled cylinders 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.

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Wikipedia