BMW R 51
Number sold 3.775
Price 1.595,- RM
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| 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 |
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| Power transmission | |
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| 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) |
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| Electrical system | |
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| Alternator | Bosch RD 50/6 2800 RS 15 |
| Ignition | battery ignition |
| Spark plugs | Bosch W 225 T 1 |
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| Suspension | |
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| 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, Ø 200 mm |
| Brakes rear | drum brake, Ø 200 mm |
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| Dimensions and weights | |
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| 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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