BMW R 51 / 3

BMW R 51 / 3 Date 1951 - 1954

Number sold 18.420

Price 2.750,- DM

Engine

Internal Designation 252 / 1
Engine type four-stroke two-cylinder flat-twin
Bore/stroke 68 x 68 mm
Cubic capacity 494 cm3
Max power 24 PS at 5800 U /min
Compression ratio 6,3 : 1
Valves per cylinder ohv
Carburation system 2 carburettor Typ Bing 1/22/41-1/22/42 or 1/22/61-1/22/62
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 4,0 / 2,28 / 1,7 / 1,3 (bis Ende 1951: 3,6 / 2,28 / 1,7 / 1,3)
Rear wheel ratio 1 : 3,89 (with sidecar 4,75 : 1)
Bevel/crown wheel 9 / 35 teeth (with sidecar 7 / 32)

Electrical system

Alternator Noris 6 Volt L 45/60 L
Ignition magneto ignition
Spark plugs Bosch W 240 T 1

Suspension

Designation 251/3 (1951), 251/4 (1952/53), 251/4 (1954)
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 (1952: Duplex, 1954: full hub)
Brakes rear drum brake, 200 mm (1954: full hub)

Dimensions and weights

Length x width x height 2130 x 790 x 985 mm
Wheel base 1400 mm
Tank capacity 17 l
Unladen weight, full tank 190 kg (with orig. BMW sidecar 320 kg)
Load rating 355 kg (with orig. BMW sidecar 600 kg)
Fuel consumption ca. 4,5 l / 100 km
Oil consumption ca. 0,7l / 1000 km
Top speed 135 km/h (with orig. BMW sidecar 95 km/h)

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