EXCELSIOR

500 TT - 1934

Going it alone

Even though Excelsior is best remembered for its success in the 250cc class – particularly for Sid Gleave's victory in the 1933 Isle of Man Lightweight TT with the stunning four-valve Mechanical Marvel -–the Birmingham firm also raced 500s in the early 1930s.

A Superb Machine

The unsuccessful use of 500cc JAP engines from 1931 until 1933 prompted Excelsior to build its own power unit for the 1934 season. The result was this superb machine, with an engine designed by Alan Bruce and closely inspired by the JAP 500 single. Its distinguishing features were a triple oil pump and twin spark plugs, each with its own magneto. Both were mounted on the right-hand side of the crankcase and driven by bevel gearing from the end of the crankshaft.

Unique Example

In 1935, Excelsior even tried mounting two carburetors on the same intake pipe. The cylinder head was made of an alloy of bronze and aluminum. The cylinder itself, held down by six studs, was aluminum with an iron liner. The engine, linked to a separate Albion gearbox, was mounted in a very classic cycle part with a Webb-type fork and rigid rear end. Less common was the rev-counter set into the fuel tank. While it was hardly in the best position to be read clearly, most riders of the period mistrusted such instruments anyway. Just one example of the 500 was built for the 1934 TT and ridden by Ted Mellors. But this well-known rider was never up among the leaders and was eventually forced to abandon the race.

SPECIFICATIONS

Engine: 498cc (80x99mm) air-cooled single-cylinder four-stroke

Power Rating: 36 hp @ 6200 rpm

Valves: overhead

Fuel System: Amal "prayer book" type carburetor (two carburetors in 1935)

Transmission: 4-speed foot-shift, chain final drive

Suspension: girder forks (front); rigid (rear)

Brakes: drum (front & rear)

Wheels: 21 inch (front); 20 inch (rear)

Weight: 322 lb

Maximum Speed: 108 mph

This superb machine had no successor; Excelsior would follow a more original course with its later competition models.