BMW M2B15

BMW M2 B15
BMW M2 B15
	BMW M2B15 at Deutsches Museum
Overview
Manufacturer	BMW
Also called	Bayern-Kleinmotor,[1]; Bayern Motor[2]
Production	1920–1923[3]
Layout
Configuration	flat-twin[4]
Displacement	494 cc (30.1 cu in)
Cylinder bore	68 mm (2.7 in)[4]
Piston stroke	68 mm (2.7 in)[4]
Cylinder block material	cast iron[4]
Cylinder head material	cast iron, in unit with block[4]
Valvetrain	side-valve pushrod engine[4]
Combustion
Fuel system	BMW carburettor[1]
Fuel type	petrol
Oil system	wet sump[1]
Cooling system	air-cooled
Output
Power output	6.5 hp (4.8 kW)[2]
Dimensions
Dry weight	31 kg (68 lb)[1]

The BMW M2B15 was BMW's first flat-twin engine.[3] 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.[5]

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,[3] and other manufacturers such as SMW and Bison also fitted it.[5]

Bayerische Flugzeugwerke used the M2B15 engine in their Helios motorcycle. BMW inherited the Helios when it was merged with BFW in 1922.[2][4]

References

Translation of BMW M2 B15 owner's manual
Norbye, Jan P. (1984). "The Origins of BMW: From Flying Machines to Driving Machines". BMW - Bavaria's Driving Machines. New York, NY, USA: Beekman House. pp. 14–17. ISBN 0-517-42464-9.
"M 2 B 15 "Small Bavarian Engine" (M15a)". BMW Classic: BMW History. Munich, Germany: BMW Group Classic. Retrieved 2012-08-11. Construction time: 1920 - 1923
Faloon, Ian (Feb 15, 2009). The BMW Boxer Twins Bible: All Air-Cooled Models 1970-1996 (Except R45, R65, G/S & GS). Veloce Publishing. pp. 6–7. ISBN 978-1-84584-1-683. Coincidentally, BMW was also interested in motorcycles and in 1920 its foreman, Martin Stolle, stripped down his 1914 Douglas 500cc flat twin. Friz set about copying it, with a few modifications, and the BMW M2 B15 engine was born.
Walker, Mick (2005-09-01). "1: Background". How To Restore Your BMW Twin: 1955-1985. Motorbooks Workshop (2nd ed.). p. 9. ISBN 978-0-7603-2262-8. Retrieved 2012-08-11. The M2B15 was supplied to Victoria, Bison, SMW and SBD and other smaller companies.

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[Manual-1] Translation of BMW M2 B15 owner's manual

[ConsGuideBMW-2] Norbye, Jan P. (1984). "The Origins of BMW: From Flying Machines to Driving Machines". BMW - Bavaria's Driving Machines. New York, NY, USA: Beekman House. pp. 14–17. ISBN 0-517-42464-9.

[BMWClassicM2B15-3] "M 2 B 15 "Small Bavarian Engine" (M15a)". BMW Classic: BMW History. Munich, Germany: BMW Group Classic. Retrieved 2012-08-11. Construction time: 1920 - 1923

[BMWBoxerBible6-4] Faloon, Ian (Feb 15, 2009). The BMW Boxer Twins Bible: All Air-Cooled Models 1970-1996 (Except R45, R65, G/S & GS). Veloce Publishing. pp. 6–7. ISBN 978-1-84584-1-683. Coincidentally, BMW was also interested in motorcycles and in 1920 its foreman, Martin Stolle, stripped down his 1914 Douglas 500cc flat twin. Friz set about copying it, with a few modifications, and the BMW M2 B15 engine was born.

[RestoreBMWTwin-5] Walker, Mick (2005-09-01). "1: Background". How To Restore Your BMW Twin: 1955-1985. Motorbooks Workshop (2nd ed.). p. 9. ISBN 978-0-7603-2262-8. Retrieved 2012-08-11. The M2B15 was supplied to Victoria, Bison, SMW and SBD and other smaller companies.