EXCELSIOR

250 Manxman Four-Valve - 1936

Built for the TT

In 1933 and 1934, the English Excelsior marque shone with its "Mechanical Marvel", an ohv 250 whose engine was built by Blackburne. When its rivals began to outclass it in terms of speed, Excelsior replaced the Blackburne unit with an in-house ohc engine. Sadly, the first engine, built in 1935, with only two valves and a very long stroke (63x79mm), proved a total failure.

New for 1936

In 1936, Tyrell Smith, famed for his success riding works Rudges, joined Excelsior and developed a new Manxman with Alan Bruce, a highly-experienced rider-engineer.

Rudge Patent

Bruce chose virtually square engine dimensions and opted for four radially-mounted valves – compelling Excelsior to pay royalties to Rudge, which had patented this configuration. Unlike the pushrod Rudge, the valves of the Excelsior were actuated by an overhead-camshaft with enclosed rockers. The head was bronze, and the modern bottom-end had an aluminium connecting rod with an automobile-type big-end. This ohc Excelsior was only just ready in time for the final practice session of the 1936 TT, but Tyrell Smith managed to finish second in the Lightweight TT. Then he won a stunning victory in the German GP on the Sachsenring, after the retirement of the works teams of DKW, Guzzi and Benelli. Further successes followed in 1937, when Tyrell Smith was joined by Ginger Wood, with second places in the Isle of Man TT, Ulster Grand Prix and Dutch TT, with a record lap of 90 mph, which was not broken until 1952!

SPECIFICATIONS

Engine: 249cc (67x71mm) air-cooled single-cylinder four-stroke

Power Rating: 22 hp @ 8000 rpm

Valves: overhead-camshaft, 4 radial valves

Fuel System: Double carburetor (originally Bowden, later Amal)

Transmission: separate Albion 4-speed, chain drive

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

Brakes: drum (front & rear)

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

Weight: 300 lb

Maximum Speed: 100 mph

Reliable as well as rapid, the 1936 four-value Excelsior works 250 gave Tyrell Smith a winning ride in that year's German Grand Prix, much to DKW's annoyance.