Sunbeam Motorcycles

Today in Motorcycle History

Sunbeam Model 9 500cc OHV

Introduced in 1924, the Model 9 and the Model 11 Sprint shared the first Sunbeam OHV 500cc engine. The Model 9 was a road-going development of the factory racing machines which had won the Isle of Man TT four times. 350cc versions of these were also offered, the Model 8 and the Model 10.

The Model 9 493cc OHV engine has three ball-race main bearings, a roller big-end bearing, dry-sump lubrication and a primary chain enclosed in a cast alloy case and running through an oil bath.

The three-speed gearbox was available in a variety of ratio options, two of which were intended for sidecar applications.

From 1924 through to 1926 the front downtube of the Model 9 frame forked just below the tank to enable the exhaust header pipe from the central exhaust port to pass between the two frame tubes. From 1927, the exhaust port was angled to the left of a single downtube and a similar Model 90, so named because it could reach 90mph (145kph), was introduced with a twin-port cylinder head and the two exhaust pipes passing either side of the front downtube.

The Model 9 was available from 1924 to 1937. It was joined by the Model 90 in 1927 and the 596cc Model 9A in 1932.