Phil Hawksley's BM Bikes

'The Ultimate BMW Information Site'

The BMW Club

Find Information, Specifications and Images of Your Favourite BMW Motorcycle

Back to index

BMW R42 Specifications

 Download

Start of Production

1926

BMW R42

Click to View

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