Retrospective: Vincent Series C Comet 500cc: 1949-1954

(This Retrospective article was published in the May 2006 issue of Rider.)

Most Americans are well familiar with the mythologized Vincent Black Shadow, but few know that the company built a big thumper, too.
Right after World War II, 500cc OHV singles were very popular in England, torquey monsters that were not too costly and fit into a relatively inexpensive taxation bracket.

In the late 1940s most mainstream British motorcycle manufacturers had a big single in the line. BSA had the B32, Velocette the MSS, Norton the ES2, Ariel the Red Hunter, etc. Some were plodders, good for going to work and hauling sidecars, others were sporty, with higher compression and more horsepower.

Phil Vincent was a bright young college graduate when he convinced his father to buy the moribund HRD motorcycle company in 1928, which built single-cylinder motorcycles using mostly JAP motors. Vincent’s big idea was for a sprung rear frame, and he continued using proprietary engines as he fiddled with the chassis. However, in 1934 he began producing an all-new single-cylinder OHV engine. The camshaft was mounted high in the right-side case, which shortened the valve train, and the pushrod tubes were splayed apart at about 60 degrees, which would soon come to identify all Vincents. This engine was bolted vertically into an open frame using the engine as a stressed member, with Vincent’s patented triangulated suspension at the rear; on the front was the well-known, friction-damped Brampton girder fork. The 499cc engine had an 84mm bore, 90mm stroke, which would remain the Vincent cylinder size for the next 26 years. It came in two guises, the 25-horsepower Meteor, and the 26-horsepower Comet.

1952 Vincent Series C Comet.
1952 Vincent Series C Comet.

Two years later the 998cc, V-twin Rapide appeared, essentially two cylinders mounted on the same crankcase, with 47 degrees between them. Legend has it that two blueprints of the single happened to be laid one on top of the other, and Vincent realized that he could easily make a twin; an entertaining but doubtful story. The added power necessitated a purpose-built clutch and transmission, an expensive operation but worth the cost, as the Rapide was soon getting the reputation of being the fastest production motorcycle available.

Then came World War II, and the factory in Stevenage turned to supporting the war effort, making airplane parts and other essential items. Vincent an­nounced that after the war the company would resume building motorcycles, but only the twin, and a modified version at that. In 1946 the first Series B Rapide appeared, in what was called a “frameless design,” with the unit-construction engine/transmission a stressed member and a square-section backbone that doubled as an oil tank. The steering head was bolted to the backbone, which was in turn bolted to the front cylinder, which was sloping forward at 25 degrees. As was the rear, as Vincent had increased the included angle of the Vee to 50 degrees. A girder fork and triangulated rear completed the chassis. There was no apparent frame visible, and the distance between the axles was an agile 56.5 inches.

1952 Vincent Series C Comet.
1952 Vincent Series C Comet.

However, this was an expensive motorcycle, costing twice as much as the competition’s 500cc singles and the Triumph twin.
Needing to fit into the money-conscious pricing structure, Vincent decided to reintroduce the single, building two versions: the low-bucks Series B Meteor, and the higher-priced Series C Comet. The singles would cost less because there would be one less cylinder, and the company could use a cheaper brought-in Burman gearbox and clutch.

The single’s new crankcases were much lighter than those of the twins, since the gearbox was now separate. To allow for the use of the Rapide-type chassis, the cylinder was canted forward at 25 degrees, just like on the twins. But how would the frameless design work, with no rear cylinder to fasten the rear suspension to? A large cast aluminum-alloy beam took the place of the missing cylinder, along with a stress-bearing primary chaincase. The chain final drive would now be on the left side, rather than on the right, as it was on the twins. Wheelbase was an even more agile 55.75 inches.

1952 Vincent Series C Comet.
1952 Vincent Series C Comet.

The Meteor used the old Brampton fork, and the engine was tuned softly, with a 11⁄16 Amal carburetor and a 6.45:1 compression ratio, putting out 26 horsepower at 5,300 rpm. This model, it should be noted, lasted less than two years before being dropped, as customers who were motivated by cost could always find cheaper.

The good stuff went into the Comet, with the new Girdraulic fork being the most obvious improvement to this new series. This fork combined both girder and hydraulic design, and could be easily adjusted for sidecar use. The Amal carb was upped to 11⁄8 size, and the engine compression ratio was increased to 6.8:1, being mindful of the low-octane gas that the Brits were using in the aftermath of World War II. On the Comet engine both cylinder and cylinder head were of aluminum, with a cast-iron liner in the barrel. Each valve had two guides in the head to keep it straight, and triple springs, ensuring good seating.

1952 Vincent Series C Comet.
1952 Vincent Series C Comet.

Hangers came down from the alloy beam, and the footpegs were at the bottom, putting the rider in a crouch that felt very comfortable above 60 mph. The saddle was the specially designed Feridax Dualseat, which was almost an integral part of the suspension design; no aftermarket saddles for this baby.

Ignition was by Lucas magneto, and the six-volt battery was charged by a Miller 50-watt dynamo. The front tire was a 3.00 x 20, the rear a 3.50 x 19. The wheels were of the QD (Quickly Detach­able) variety, in case of flat tires, and the rear had a centerstand to aid this operation. There were two sidestands, one on each side of the engine. This being the era of skinny brake drums, Vincent solved the stopping problem by putting two drums on each wheel—no motorcycle in those years stopped as well as a properly fettled Vincent.

1952 Vincent Series C Comet.
1952 Vincent Series C Comet.

Dry weight was a modest 390 pounds, and a well-running Comet could easily see 90 mph on the Smiths 120-mph speedometer. This was for the sporting rider, not the plodder. As one road-tester wrote in 1950, “At larger throttle openings the exhaust note possessed a crisp, taut note that, in town, may have attracted some attention, but seemed to add to the enjoyment of the ride in the open country.”

The Comet was not cheap, but there was enough demand to keep it in production until the Series C line ended its run in 1954. A year later the factory closed.


  1. The first motorcycle I owned was a 1963 series C Comet. I had learned to tide on a friends Triumph T100 and believe that the Vincent,s handling left the Triumph for dead. My wife and I travelled many miles on the Vincent and both felt safe and comfortable in all conditions. While the bike may not have been as fast on the straight as some 500cc twins it left them for dead in fast corners due to its excellent suspension. I found it easy to service and maintain and, if I ever win the lottery, I will be looking to buy a rebuilt Comet at any price.

  2. Hi I have bought a second Comet my first of 1951 vintage NKN112 is in Australia Ken Phelps has had her since 1974, I on my 72nd birthday took possession of TVK960 she had been in a museum for a little short of 30 years, now in my garage being sorted out for the road I am looking forward very much to getting out there again on a Comet. but first to get her into great shape.


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