BMW R 51

BMW R 51 Date 1938 - 1940

Number sold 3.775

Price 1.595,- RM

Engine

Internal Designation 254 / 1
Engine type four-stroke two-cylinder flat-twin
Bore/stroke 68 x 68 mm
Cubic capacity 494 cm3
Max power 24 PS at 5600 U /min
Compression ratio 6,7 : 1
Valves per cylinder ohv
Carburation system 2 carburettor Typ Amal 5 / 423
Engine lubrication forced-feed lubrication
Oil pump gear pump

Power transmission

Clutch single discs, dry
Number of gears 4
Shifting foot Shifting (+ auxiliary manual lever on the gear block)
Gear ratios 3,6 / 2,28 / 1,7 / 1,3
Rear wheel ratio 1 : 3,89 (sidecar 1 : 4,62)
Bevel/crown wheel 9 / 35 teeth (sidecar 8 / 37)

Electrical system

Alternator Bosch RD 50/6 2800 RS 15
Ignition battery ignition
Spark plugs Bosch W 225 T 1

Suspension

Designation 251 / 1
Type of frame twin-loop steel tubular frame
Front suspension telescopic fork
Rear suspension telescopic fork
wheel rims deep-bed 3 x 19
Tyres front 3,50 x 19
Tyres rear 3,50 x 19
Brakes front drum brake, 200 mm
Brakes rear drum brake, 200 mm

Dimensions and weights

Length x width x height 2130 x 815 x 960 mm
Wheel base 1400 mm
Tank capacity 14 l
Unladen weight, full tank 182 kg
Load rating 210 kg ((max. overall weight with sidecar 500 kg)
Fuel consumption ca. 4 l / 100 km
Oil consumption ca. 1 l / 1000 km
Top speed 140 km/h (with sidecar 110 km/h)

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