1937 BMW R12 Twin carb Technical Analysis & Specification Breakdown
Engineered by BMW for the sport motorcycle segment, the 1937 BMW R12 Twin carb features a 745 cc (45.5 cu in) air-cooled two cylinder boxer, four-stroke configuration. In factory specification, peak output is rated at 20 HP (14.6 kW) at 4,000 rpm, transferring power to the rear wheel through a 4-speed gearbox. With a specific output of 26.8 HP per liter, the engine character is prioritizing low-RPM tractability, mechanical longevity and relaxed throttle response over peak redline numbers.
On the scales, the R12 Twin carb measures 185 kg (408 lbs) wet (curb), translating to a power-to-weight ratio of 0.11 HP/kg (9.25 kg per horsepower). The 14-liter (3.7 US gal) fuel tank paired with a rated consumption of 4.5 L/100 km provides an estimated theoretical range of roughly 311 km (193 miles) between fill-ups, while factory top speed is listed at 120 km/h (75 mph).
Within MotoLibrary's BMW archive, this model family spans 8 indexed model years from 1935 to 1942, allowing buyers to track year-over-year changes in emissions tuning, weight and equipment.
Specific Output
26.8 HP/L
Power-to-Weight
0.11 HP/kg (9.25 kg/HP)
Theoretical Range
~311 km (193 mi)
Engine
Displacement745.0 ccm (45.46 cubic inches)
Engine TypeTwo cylinder boxer, four-stroke
Engine DetailsTwo cylinder boxer, four-stroke
Power20.0 HP (14.6 kW)) @ 4000 RPM
Compression5.2:1
Bore x Stroke78.0 x 78.0 mm (3.1 x 3.1 inches)
Fuel SystemCarburettor. Amal
Fuel ControlOverhead Valves (OHV)
LubricationWet sump
CoolingAir
Transmission
Gearbox4-speed
ClutchDry multiplate-cable operated
Performance
Top Speed120.0 km/h (74.6 mph)
Fuel Consumption4.50 litres/100 km (22.2 km/l or 52.27 mpg)
Greenhouse Gases104.4 CO2 g/km. (CO2 - Carbon dioxide emission)
Use this page to compare this motorcycle by its real specifications, not only by model name. Focus on the details that affect fit, comfort, handling, range and ownership.
Power
Compare engine output with similar motorcycles if acceleration, highway use or two-up riding matters.
Fuel Capacity
Fuel capacity helps estimate touring range and how often you may need to stop.
Brakes
Brake setup is worth comparing if you ride in traffic, mountains or with a passenger.
Suspension
Suspension details can matter for comfort, road feel and long-distance riding.
Transmission
Transmission and final drive affect maintenance, smoothness and everyday usability.
