Model: R 42
Production  
Engine  
Power transmission  
Electrical System  
Chassis  
Dimensions/Weights  
     
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Production
Begin of the Production   1925
End of the Production   1927
Numbers Produced   855
Price   1.870,- RM
Engine
Internal Designation   M 40
Motor Type   four-stroke single-cylindervertical
Bore x Stroke   68 x 68 mm
Displacement   247 ccm
Max Power   6,5 hp at 4500 rpm
Compression Ratio   6.0 : 1
Valves   ohv
Carburetion System   1 x carburettor BMW Spezial 20 mm
Engine Lubricating System   forced-feed lubrication
Oil Pump   gear pump
Power Transmission
Clutch   single-plate, dry
Number of Gears   3
Shifting   manual
Gearbox Ratios   6 / 9.28 / 13.7
Rear Wheel Ratio   1 : 2.84
Bevel / Crownwheel   14 / 37 teeth
Electrical System
Ignition System   Bosch magneto generator type G 1.8 V/15 W
Generator   Bosch magneto ignition
Spark Plugs   Bosch W 175
Chassis
Designation   R 39
Frame   twin-loop tubular frame
Front Wheel Suspension   plate spring, 4 laminae
Rear Wheel Suspension   rigid
Wheel Rims   27 x 3.5 type CC I
Tyres front   27 x 3.5 balloon or with 26 x 3 high-pressure tyres
Tyres rear   27 x 3.5 balloon or with 26 x 3 high-pressure tyres
Brakes front   internal shoe brake (drum brake) Ø 150 mm
Brakes rear   external shoe brake at the gearing (on cardan shaft)
Dimensions/Weights
Length x Width x Height   2050 x 800 x 950 mm
Fuel Tank Capacity   10 l
Unladen Weight, Full Tank   110 kg
Fuel Consumption   approx. 2,5 l/100 km
Oil Consumption   approx. 1-2 l/1000 km
Top Speed   100 kph