NSU 1932 501 OS 494 cc 1 cyl OHV 3605

NSU 1932 501 OS 494 cc OHV two-port frame # 857234 engine # 160754

Walter Moore, responsible for the Norton racing department, had developed the 500cc Norton CS1 and the 350cc Norton CJ1. Alec Bennett won the 1927 Senior TT on such a camshaft Norton but in 1928 and 1929 Norton performed very poorly in the Isle of Man TT. Consequently, relations between Moore and Norton management soured; they already had two successors (Joe Craig and Arthur Carroll) lined up. Meanwhile, NSU had little to offer in the German championship against the fast BMWs of Ernst Henne and Hans Soenius. Chief designer Otto Reitz was looking for a solution and turned to Walter Moore, who moved to Neckarsulm in 1929. Moore had already started designing a new engine in his spare time in 1927 as a replacement for the CS1, and this was now used for the new NSU, the SS 500.
The SS 500 had slightly different bore x stroke dimensions than the Norton racers, but looked outwardly rather similar, which earned the make the nickname “Norton Spares Used” in the UK. The SS 500 was sold as a fast sports model, but was too expensive and too fragile for daily use on the road. Subsequently Moore designed a line of sporty OHV machines in various capacities with the designation “OS” or “Obengesteuert Sport” , the “O” standing for “Overhead valves”. The engine design closely followed the lines of the SS 500, giving the impression of an OHC power source. The 501 OS was the top model of the OS model range, which ran from 1932 up to including 1934. In 1935 a luxury version came out, the 501 OSL. The 494 cc engine has the same bore x stroke dimensions as the SS 500, 80 x 99 mm (the 490 cc Norton CS1 has bore x stroke of 79 x 100 mm). The engine has an output of around 20 hp and not many were sold in the economic depression years.
Our 501 OS has been in the care of the former owner since 1988. She came from Poland and was in need of restoration. This was carried out by the former owner in the early 90s, with the help of a specialist engine rebuilder who made sure the engine was properly overhauled. The gearbox was in a bad condition, and a replacement was sought and found. It’s a four-speed foot-change gearbox, available as an extra at the time. The machine features battery and coil ignition and is equipped with Bosch dynamo, Amal carb, 120 km/h speedo, steering damper, aluminium primary case and practical side stand. She has been very well kept and the former owner estimates that since restoration not much more than 5000 km have been covered, mainly in Dutch vintage club runs.