| MODEL | BMW R 4 1932 - 1937 |
| Year | 1932 - 1937 |
| Engine Type | Four stroke, single cylinder vertical, OHV, 2 valves |
| Displacement / Capacity | 398 cc / 24.3 cu in |
| Bore X Stroke | 78 x 84 mm |
| Compression Ratio | 5.7:1 |
| Cooling System | Air cooled |
| Max Power | 10.4 kW / 14 hp @ 4000 rpm (1932-1933: 12 hp @ 4000 rpm) |
| Max Torque | — |
| Ignition | Battery ignition |
| Induction | 1 x Sum CK 3/500 Fr carburettor |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4 Speed (1932: 3 Speed) |
| Clutch | Single plate, dry |
| Final Drive | Shaft |
| CHASSIS SPECS | |
| Frame | Pressed steel duplex frame |
| Front Suspension | Leaf spring fork (9 leaves) with friction dampers |
| Rear Suspension | Rigid, sprung saddle |
| Front Brakes | Drum |
| Rear Brakes | Drum |
| DIMENSION SPECS | |
| Overall Length | 1980 mm / 78.0 in |
| Overall Width | 850 mm / 33.5 in |
| Overall Height | 950 mm / 37.4 in |
| Seat Height | 700 mm / 27.6 in |
| Wheelbase | 1300 mm / 51.2 in |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | 137 kg / 302 lbs |
| WHEEL SPECS | |
| Front Tyre | 3.50 x 26" |
| Rear Tyre | 3.50 x 26" |
| FUEL SYSTEM | |
| Fuel Capacity | 12 Litres / 3.2 US gal (1932-1933: 10 Litres / 2.6 US gal) |
| Fuel Consumption | 3.5 L/100 km / 67 mpg US |
| Top Speed | 100 km/h / 62 mph |
The R 4 grew out of the R 2 as a 400 cc single that filled the gap below the 750 cc twins. Rugged and economical, it became a favourite of the German army, police and other state buyers, who took several thousand. Through five series it gained a four-speed gearbox, a larger tank and a rise from 12 to 14 hp, and around 15,000 were built by 1937.
