The Vincent That Never Was: Comet SS

Vincent Series D enthusiast Tony Cording and friends build the ultimate Vincent single: a Series D Comet Super Sport.


Vincent Comet SS

Engine: 636cc air-cooled OHV 4-stroke single, 90mm x 100mm bore and stroke, 10:1 compression ratio, 45hp (calculated)
Top speed: 115mph (est.)
Carburetion: 36mm Mikuni
Transmission: 4-speed Norton gearbox, chain final drive
Electrics: 12v generator, BT-H electronic magneto
Frame/wheelbase: 1-inch-diameter steel tube backbone w/engine as a stressed member
Suspension: Vincent Girdraulic front, Vincent swing fork, single spring/damper unit rear
Brakes: Three 7in (178mm) SLS drums, two front, one rear
Tires: 100/90 x 19in front, 110/90 x 18in rear
Weight: 375lb (170kg)
Seat height: 31in (787mm)
Fuel capacity/MPG: 5gal (18.9ltr)/50-60mpg

Although best known for its thundering V-twins, Vincent always included a 500cc single in its model range. That is, until the Series D models of 1955.

The 636cc single is fed by a 36mm Mikuni carb.

Vincent showed two prototypes of a Series D single — the fully enclosed Victor and a naked Comet — but neither went into production. Series D enthusiast Tony Cording decided he would build his own. First, though, a little history.


In the decade after World War II, Vincent’s position as builder of the world’s fastest street bike was threatened by ever-quicker and more powerful parallel twins. First BSA then Triumph established record speeds of over 150mph on the salt. The Rapide’s 45 horsepower and the Shadow’s 55 horsepower were impressive — as was their unmatched torque — but by 1955, a street Tiger 110 was making 40 horsepower and BSA’s Super Flash claimed 42 horsepower, with more to come. Vincent’s rear suspension was no longer unique with the almost universal adoption of swinging fork style suspension. While the quality of design and build of the Vincent was unparalleled, the competition was improving all the time.

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