Although BMW can trace its heritage back to before WWI, it was the post-First World War company that begins the motorcycle story.
During the first World War, the predecessor of BMW, Rapp Motorenwerke, produced aircraft engines. However, after the signing of the Treaty of Versailles, the Germans were not allowed a military air force, nor were they allowed to build aircraft in Germany. With their highly skilled workforce ideally suited to the manufacture of engines and motorized vehicles, the obvious new direction for the company was the production cars and motorcycles.
First Motorcycle Engines
Although the First World War ended in 1918, it took the company another two years to reorganize to the point that they could offer their first motor—a 148-cc unit called the Kurier. A year later, the first flat-twin engine was developed. The M2 B15 was the first of the most famous BMW engines, best known as the Boxer.
In 1922, BMW merged with one of their customers, Bayerische Flugzeugwerke. This merger set the company on the road to becoming one of the world’s major motorcycle manufacturers. Just a year after the merger (1923) the company offered the first complete BMW motorcycle with its famous across the frame flat-twin boxer engine: the R32. The new machine had exceptional performance, for the time, with a top speed around 60 mph (95 kph). The engine had a revolutionary oiling system which recirculated oil that had been collected and filtered in a bottom (sump) section. (This was at a time when other manufacturers were still using a total loss oiling system.)
The BMW proved to be very successful both in retail market and also in various competitions—something most the manufacturers did to promote their motorcycles. Major competition results included winning the Italian Targa Florio race, and also setting a new world land speed record of 134 mph (216 kph) which was set by Ernst Henne using a supercharged 750cc “compressor” machine in 1928.
The world economic downturn in the late 20s early 30s hit BMW too, forcing them to produce a smaller bike which the markets were demanding. The company responded with the R2 a 4-stroke with a capacity of 198-cc. In addition, the German army commissioned BMW to produce R4s (a 398-cc single cylinder OHV 4-stroke) for military use.
In 1936 the German company claimed their first Grand Prix racing success when Otto Ley won the Swedish 500-cc race using another “Kompressor” machine. The BMWs became the dominant force in GP racing until the outbreak of the Second World War, after which supper chargers were banned by the FIM (Fédération Internationale de Motocyclisme) from motorcycle racing.
During the Second World War BMW produced the R75 which, with a sidecar, was used primarily for escort duty’s, and messenger work by the army. The robust machine was often fitted with a machine gun, but at some 925 lbs (420 kgs) it was not lightweight.
Ural and BMW
Interestingly, the Russian Ural company initially collaborated with BMW in the development of a sidecar for military use (Russia and Germany were on the side at the beginning of the Second World War). In particular, the drive train was highly developed to give two-wheel-drive. This helped the sidecar get traction in such diverse conditions as deserts, snow, and mud.
As per the First World War, Germany was not allowed to produce motorcycles at the conclusion of the war. In addition, German patents were used as reparation.
By 1948 BMW had returned to producing motorcycles, albeit a R24 with a a small engine--the maximum engine size allowed at time was 250-cc.