BMW M2B15
Template:Infobox automobile engine
The BMW M2B15 was BMW's first flat-twin engine.[1] Manufactured from 1920 to 1923, the M2B15 was intended to be a portable industrial engine,[2] but it was used by several German motorcycle manufacturers to power their motorcycles.[3]
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.[4] This was referred to internally as the Type M2B15 and offered for sale officially as the "Bayern Motor".[2] The engine was tried out by various motorcycle manufacturers. Starting in 1920, Victoria of Nuremberg used the engine[2] in their KR 1 motorcycle,[1] and other manufacturers such as SMW and Bison also fitted it.[3]
Bayerische Flugzeugwerke used the M2B15 engine in their Helios motorcycle. BMW inherited the Helios when it was merged with BFW in 1922.[2][4]