R42

Start of Production

1926

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End of Production

1928

Numbers Produced

6,502

Price

1,510 RM

Engine

Internal Designation

M 43

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

12 hp at 3,400 rpm

Compression Ratio

4.9 : 1

Valves

SV

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

2.49 / 1.50 / 1.08

Rear Wheel Ratio

1 : 4.53 or 1 : 3.8 (1 : 6.27 or 1 : 5.7 with sidecar)

Bevel/Crownwheel

15 / 68 or 15 / 57 teeth (11 / 69 or 10 / 57 with sidecar)

Electrical System

Ignition System

Bosch magneto ignition

Generator

Bosch magneto generator on request

Spark Plugs

Bosch W 175

Chassis

Designation

R42

Frame

Twin loop steel tubular frame

Front wheel suspension

Plate spring, 5 laminae

Rear wheel suspension

Rigid

Wheel rims

Deep bed 19x 3 or 21x 2.5

Tyres, Front

26 x 3.5 on 19 x 3 or 27 x 2.75 on 21 x 2.5

Tyres, Rear

26 x 3.5 on 19 x 3 or 27 x 2.75 on 21 x 2.5

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

126 Kg / 277 lb (188 Kg / 414 lb with original sidecar)

Fuel Consumption

Approx. 3 litres per 100 Km / 94 mpg / 78 mpg US

Oil Consumption

Approx. 1.7 litres per 1,000 Km

Top Speed

95 Kph / 59 mph