Start of Production

1927

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End of Production

1928

Numbers Produced

1,720

Price

1,850 RM

Engine

 

Internal Designation

M 51

Motor Type

Four-stroke two cylinder flat twin

Bore x Stroke

68 x 68 mm (2.67 x 2.67 in)

Displacement

494 cc

Max Power

18 hp at 4,000 rpm

Compression Ratio

5.8 : 1

Valves

OHV

Carburation System

1 carburettor, Type BMW Spezial 2 valve 22 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

2.50 / 1.50 / 1.07

Rear Wheel Ratio

1 : 4.38 (1 : 5.7 with sidecar)

Bevel/Crownwheel

13 / 57 teeth (10 / 57 with sidecar)



Electrical System

 

Ignition System

Bosch magneto ignition

Generator

Magneto generator on request

Spark Plugs

Bosch W 175






Chassis

 

Designation

R47

Frame

Twin loop steel tubular frame

Front wheel suspension

Plate spring, 5 laminae

Rear wheel suspension

Rigid

Wheel rims

CC 1

Tyres, Front

27 x 3.5 low pressure or 26 x 3 high pressure

Tyres, Rear

27 x 3.5 low pressure or 26 x 3 high pressure

Brakes, Front

Drum brake 150 mm / 5.90 in diameter

Brakes, Rear

External shoe brake at the gearing on Cardan shaft




Dimensions/Weights

 

Length x Width x Height

2100 x 800 x 950 mm (82.67 x 31.49 x 37.40 in)

Wheel Base

1410 mm / 55.51 in

Fuel Tank Capacity

14 litres / 3.07 gal / 3.69 gal US

Unladen Weight with Full Tank

130 Kg / 286 lb (192 Kg / 422 lb with original sidecar)

Top Speed

110 Kph / 68 mph



Information kindly supplied by P.Hawksley

www.bmbikes.co.uk