BMW R 51 / 2
Number sold 5.000
Price 2.750,- DM
| Engine | |
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| internal designation | 254 / 3 |
| 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 | 6,4 : 1 |
| Valves per cylinder | ohv |
| Carburation system | 2 carburettor Typ Bing 1/22/39 und 1/22/40 |
| Engine lubrication | forced-feed lubrication |
| oil pump | gear pump |
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| Power transmission | |
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| Clutch | Einscheiben-TrockenClutch |
| 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 (with sidecar 4,57 : 1) |
| Bevel/crown wheel | 9 / 35 (with sidecar 7 / 32) |
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| Electrical system | |
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| Alternator | Bosch 6 V / 75 Watt |
| Ignition | battery ignition |
| Spark plugs | Bosch W 240 T 1 |
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| Suspension | |
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| designation | 251 / 2 |
| Type of frame | Geschlossener Doppelstahlrohrframe |
| Front suspension | telescopic fork |
| Rear suspension | telescopic fork |
| wheel rims | deep-bedwheel rims |
| Tyres front | 3,50 x 19 |
| Tyres rear | 3,50 x 19 |
| Brakes front | drum brake, Ø 200 mm (Halbnabe) |
| Brakes rear | drum brake, Ø 200 mm (Halbnabe) |
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| Dimensions and weights | |
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| Length x width x height | 2130 x 815 x 720 (saddle) mm |
| Ground clearance | 120 mm |
| Tank capacity | 14 l |
| Unladen weight, full tank | 185 kg |
| load rating | 400 kg |
| Fuel consumption | ca. 4 l / 100 km |
| oil consumption | ca. 1 l / 1000 km |
| Top speed | 135 km/h |
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