| MODEL | BMW R 51/3 1951 - 1955 |
| Year | 1951 - 1955 |
| Engine Type | Four stroke, two cylinder horizontally opposed boxer, pushrod operated OHV, single gear-driven camshaft, 2 valves per cylinder |
| Displacement / Capacity | 494 cc / 30.1 cu in |
| Bore X Stroke | 68 x 68 mm |
| Compression Ratio | 6.3:1 |
| Cooling System | Air cooled |
| Max Power | 18 kW / 24 hp @ 5800 rpm |
| Max Torque | — |
| Ignition | Magneto |
| Induction | 2 x Bing 1/22/41 - 1/22/42 or 1/22/61 - 1/22/62 carburettors |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4 Speed |
| Clutch | Single plate, dry |
| Final Drive | Shaft |
| CHASSIS SPECS | |
| Frame | Closed double loop steel tubular frame |
| Front Suspension | Telescopic fork with hydraulic damping |
| Rear Suspension | Plunger with coil springs and rubber stops |
| Front Brakes | 200 mm drum, duplex (full-width hub from 1954) |
| Rear Brakes | 200 mm drum, simplex |
| DIMENSION SPECS | |
| Overall Length | 2130 mm / 83.9 in |
| Overall Width | 790 mm / 31.1 in |
| Overall Height | 985 mm / 38.8 in |
| Seat Height | 720 mm / 28.3 in |
| Wheelbase | 1400 mm / 55.1 in |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | 190 kg / 418 lbs |
| WHEEL SPECS | |
| Front Tyre | 3.50 - 19 |
| Rear Tyre | 3.50 - 19 |
| FUEL SYSTEM | |
| Fuel Capacity | 17 Litres / 4.5 US gal |
| Fuel Consumption | 4.5 L/100 km / 52 mpg US |
| Top Speed | 140 km/h / 87 mph |
Photo: Späth Chr., Public domain, via Wikimedia Commons
Photo: Jeff Dean, Attribution, via Wikimedia Commons
Shown at the 1951 Amsterdam show beside the 600 cc R 67, the R 51/3 kept the plunger-sprung chassis but had a cleaned-up engine with a single gear-driven camshaft in place of the earlier chain-driven pair. It was smooth, well-mannered and did well in the 1951 International Six Days. Running changes included improved brakes, fork gaiters and, for 1954, full-width hubs and alloy rims before the R 50 replaced it.
