4PS

1921 NSU 4PS Technical Analysis & Specification Breakdown

At the heart of the 1921 NSU 4PS sport motorcycle, NSU relies on a 498 cc (30.4 cu in) air-cooled twin, four-stroke powerplant. In factory specification, peak output is rated at 6.5 HP (4.7 kW) at 3,000 rpm, transferring power to the rear wheel through belt final drive. With a specific output of 13.1 HP per liter, the engine character is prioritizing low-RPM tractability, mechanical longevity and relaxed throttle response over peak redline numbers.

On the scales, the 4PS measures 120 kg (265 lbs) dry, translating to a power-to-weight ratio of 0.05 HP/kg (18.46 kg per horsepower). Rider ergonomics and chassis geometry center around a 1,415 mm (55.7 in) wheelbase engineered for quick, flickable steering geometry. The 9-liter (2.4 US gal) fuel tank supports practical everyday commuting and weekend road stints, while factory top speed is listed at 80 km/h (50 mph).

Within MotoLibrary's NSU archive, this model family spans 5 indexed model years from 1921 to 1925, allowing buyers to track year-over-year changes in emissions tuning, weight and equipment.