The BMW M2B15 was

BMW Bayerische Motoren Werke AG, trading as BMW Group (commonly abbreviated to BMW (), sometimes anglicised as Bavarian Motor Works), is a German multinational manufacturer of vehicles and motorcycles headquartered in Munich, Bavaria, Germany. Th ...

's first

flat-twin engine A flat-twin engine is a two-cylinder internal combustion engine with the cylinders on opposite sides of the crankshaft. The most common type of flat-twin engine is the boxer-twin engine, where both pistons move inwards and outwards at the same ti ...

. Manufactured from 1920 to 1923, the M2B15 was intended to be a portable industrial engine, but it was used by several German motorcycle manufacturers to power their motorcycles. In 1920, BMW engineer Max Friz reverse-engineered the engine of foreman Martin Stolle's 1914 Douglas motorcycle and developed a similar 500 cc side-valve flat engine from it. This was referred to internally as the Type M2B15 and offered for sale officially as the "Bayern Motor". The engine was tried out by various motorcycle manufacturers. Starting in 1920, Victoria of

Nuremberg Nuremberg (, ; ; in the local East Franconian dialect: ''Nämberch'' ) is the Franconia#Towns and cities, largest city in Franconia, the List of cities in Bavaria by population, second-largest city in the States of Germany, German state of Bav ...

used the engine in their KR 1 motorcycle, and other manufacturers such as SMW and Bison also fitted it. Bayerische Flugzeugwerke used the M2B15 engine in their Helios motorcycle. BMW inherited the Helios when it was merged with BFW in 1922.

References

M2B15 Motorcycle engines Boxer engines {{Motorcycle-stub