| MODEL | BMW R 51/2 1950 - 1951 |
| Year | 1950 - 1951 |
| Engine Type | Four stroke, two cylinder horizontally opposed boxer, pushrod operated OHV, 2 valves per cylinder |
| Displacement / Capacity | 494 cc / 30.1 cu in |
| Bore X Stroke | 68 x 68 mm |
| Compression Ratio | 6.4:1 |
| Cooling System | Air cooled |
| Max Power | 18 kW / 24 hp @ 5800 rpm |
| Max Torque | — |
| Ignition | Bosch coil, manual advance by handlebar lever |
| Induction | 2 x Bing Spezial 1/22/29 and 1/22/30 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 |
| Rear Suspension | Plunger with coil compression springs and rubber stops |
| Front Brakes | 200 mm drum, duplex |
| Rear Brakes | 200 mm drum, simplex |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | — |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | 185 kg / 407 lbs |
| WHEEL SPECS | |
| Front Tyre | 3.50 - 19 |
| Rear Tyre | 3.50 - 19 |
| FUEL SYSTEM | |
| Fuel Capacity | 14 Litres / 3.7 US gal |
| Fuel Consumption | — |
| Top Speed | 135 km/h / 83 mph |
The R 51/2 of 1950 was BMW's first post-war twin, essentially the pre-war R 51 rebuilt once Allied limits on engine size were eased. The easiest way to spot it is its split rocker covers held by a clip. Period testers liked its smooth engine and stable handling but found the front brake weak; it was replaced after a single production run by the redesigned R 51/3.
