BMW R51

Start of Production 1951 Click to View End of Production 1954 Numbers Produced 18,420 Price 2,750 DM Engine Internal Designation 252/1 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 24 hp at 5,800 rpm Compression Ratio 6.3 : 1 Valves OHV Carburation System 2 x carburettor type Bing 1/22/41 - 1/22/42 or 1/22/61 - 1/22/62 Engine Lubricating System Forced feed lubrication Oil Pump Gear pump Power Transmission Clutch Single plate, dry Number of Gears 4 Shifting Foot shifting (+ auxiliary manual lever on the gear block) Gearbox Ratios 4.0 / 2.28 / 1.7 / 1.3 ('till the end of 1951: 3.6 / 2.28 / 1.7 / 1.3) Rear Wheel Ratio 1 : 3.89 (1 : 4.75 with sidecar) Bevel/Crownwheel 9 / 35 teeth (7 / 32 with sidecar) Electrical System Ignition System Magneto ignition Generator Noris 6 V L 45/60 L Spark Plugs Bosch W 240 T1 Chassis Designation 251/3 (1951), 251/4 (1952/53), 251/4 (1954) Frame Double loop steel tubular frame Front wheel suspension Telescopic fork Rear wheel suspension Telescopic suspension Wheel rims 3 x 19 deep bed Tyres, Front 3.5 x 19 Tyres, Rear 3.5 x 19 Brakes, Front Drum brake 200 mm / 7.87 in diameter (1952:duplex, 1954: full hub) Brakes, Rear Drum brake 200 mm / 7.87 in diameter (1954: full hub) Dimensions/Weights Length x Width x Height 2130 x 790 x 985 mm (83.85 x 31.10 x 38.77 in) Wheel Base 1400 mm / 55.11 in Fuel Tank Capacity 17 litres / 3.73 gal / 4.49 gal US Unladen Weight with Full Tank 190 Kg / 418 lb (with original sidecar, 320Kg / 704 lb) Idle/Riding Noise 84 / 94 phon (from 7/7/1953: 81 / 85 phon) Load Rating 355 Kg / 781 lb (with original sidecar, 600 Kg / 1321 lb) Fuel Consumption 4.5 litres 100Km approx. / 62 mpg / 52 mpg US Oil Consumption 0.7 litre per 1,000 Km approx. Top Speed  source 135 Kph / 83 mph (95 Kph / 59 mph with original sidecar)