| MODEL | BMW R 42 1926 - 1928 |
| Year | 1926 - 1928 |
| Engine Type | Four stroke, two cylinder horizontally opposed boxer, side valve (SV) |
| Displacement / Capacity | 494 cc / 30.1 cu in |
| Bore X Stroke | 68 x 68 mm |
| Compression Ratio | 4.9:1 |
| Cooling System | Air cooled |
| Max Power | 8.9 kW / 12 hp @ 3400 rpm |
| Max Torque | — |
| Ignition | Bosch magneto ignition |
| Induction | 1x BMW Spezial 22 mm |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 3 Speed, hand shift |
| Clutch | Single plate saucer spring, dry |
| Final Drive | Shaft |
| CHASSIS SPECS | |
| Frame | Twin loop steel tubular frame |
| Front Suspension | Trailing link with leaf spring, 5 laminae |
| Rear Suspension | Rigid, spring loaded saddle |
| Front Brakes | 150 mm drum |
| Rear Brakes | External shoe brake on the drive shaft |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | 720 mm / 28.3 in |
| Wheelbase | — |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | 126 kg / 278 lbs |
| WHEEL SPECS | |
| Front Tyre | 27 x 3.5 low pressure or 26 x 3.0 high pressure |
| Rear Tyre | 27 x 3.5 low pressure or 26 x 3.0 high pressure |
| FUEL SYSTEM | |
| Fuel Capacity | 14 Litres / 3.7 US gal |
| Fuel Consumption | 3 L/100 km |
| Top Speed | 95 km/h / 59 mph |
The R 42 succeeded the R 32 as BMW's touring twin, keeping the side-valve boxer layout and frame but with output raised to 12 hp. A brake acting on the drive shaft replaced the old wedge-block rear brake, and a 30 percent price cut more than doubled sales to over 6,500 units.
