| MODEL | NSU 251 S 1926 - 1929 |
| Year | 1926 - 1929 |
| Engine Type | Single cylinder, 4-stroke, overhead valve |
| Displacement / Capacity | 247 cc / 15.1 cu in |
| Bore X Stroke | 63 mm x 80 mm |
| Compression Ratio | — |
| Cooling System | Air-cooled |
| Max Power | 11.8 kW / 16 hp @ 4400 rpm |
| Max Torque | — |
| Ignition | Magneto |
| Induction | — |
| Start System | — |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 3-speed |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | Light closed double-tube |
| Front Suspension | Spring-loaded fork |
| Rear Suspension | — |
| Front Brakes | — |
| Rear Brakes | — |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | — |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | — |
| Rear Tyre | — |
| FUEL SYSTEM | |
| Fuel Capacity | — |
| Fuel Consumption | — |
| Top Speed | 100 km/h / 62 mph |
A sporting overhead-valve development of NSU's side-valve 250 touring single, with reworked rods, pistons and cylinder for much more output. Privateer Franz Islinger won the 1926 German 250 cc championship on one, and a revised lubrication system arrived in 1928.
