Did Rodney Dangerfield ride a thumper? After all, single-cylinder engines just don’t get no respect. Last week, we told you about a made-in-Sweden attempt to build a modern Supermono-style single-cylinder engine based off Buell’s Helicon V-twin, but that’s a niche project. When was the last time you saw a single-cylinder class in World Supersport or MotoGP? Even the Isle of Man ditched the Singles TT race back in 2000.
It’s a bummer, because singles have lots to offer: light weight, usable torque, mechanical simplicity, and a proud history. After World War II, the Euro manufacturers’ lineups were all based around singles, ranging from el cheapo grocery-getters to bikes like the Vincent Comet. The Vincent Comet offered high performance at a lower price than the company’s V-twins, a sort of sensible performance bike. A fast machine in its day, it’s practically forgotten in our modern era.
A single solution
As Vincent’s Stevenage factory rebooted its production after World War II, the bigwigs realized they had a problem: Their bikes were too expensive, which hurt sales. The solution? Bring back the its single-cylinder models, which had been the foundation of the Vincent lineup before the war. Theoretically, Vincent could lower its prices while still offering superior engineering.
Vincent revived two new single-cylinder models out for the late 1940s, the Comet and the Meteor. The Meteor was lower-priced, with lower performance to match. The Comet came with a higher price tag, and more muscle packed into the engine.
Both these machines were built around air-cooled 499 cc single-cylinder engines. This engine itself was an in-house development. Legendary motorcycle designer Phil Irving and owner Philip C. Vincent had put together the factory’s first self-built design in 1934. Previously, Vincent had used engines sourced from other Brit manufacturers, a very common practice in those days.
The post-war singles had mechanical upgrades, and some cost-cutting measures. Vincent’s pre-war V-twins were improvements on the single-cylinder designs. Its post-war singles saw the lessons learned on the V-twin series then applied to the Series C Comet engines. The Series C engine actually shared many internals with the V-twin series, and like modern Supermono concepts, it’s considered fairly tough as a result.
One of the most notable differences between the cheaper singles and Vincent’s pricier V-twins is the gearbox. Vincent went with a four-speed gearbox and clutch from Burman, which saved some money. The engine internals were generally not fettled to the same level as the Rapide, Black Shadow or other performance models.
That didn’t stop the pushrod/OHC engine from making decent power, though. Plenty of online moto-pundits rate these for 28 horsepower, but the Series C engine responded well to careful tuning, like all Brit bikes. Boosting compression could give you more speed. But do you even need it? Back in the ’50s, riders were pushing these bikes to 90 mph and even beyond. Even today, that’s respectable for an air-cooled 500 cc thumper.
Also, remember that while Vincent was probably building the most modern chassis on the market at that time (based off the Rapide series), it’s still a 1950s design. The Comet came with the engine as a stressed member (very forward thinking in the 1950s!), dual front drum brakes, a Girdraulic fork (girder fork with hydraulic damping), and cantilever rear suspension setup. This was top-shelf design in its era, but is definitely crude by today’s standard.
Realistically, these are all collector bikes at this point, and they fetch so much coin that most owners aren’t anxious to try to do the ton, especially on open roads.
This machine here
This 1951 Series C Vincent Comet is for sale on Bring a Trailer, with the auction ending in a couple of days. At first glance, it appears like a well-sorted restoration. The ad says the seller acquired the machine in 2017, and completed a restoration this year. The engine got “a refreshed cylinder head, along with a replacement crankshaft, single Amal side-bowl carburetor, oil pump, BTH Components magneto, and bearings.” The engine’s numbers match the frame, which was also refurbished. The fuel tank was repainted black, with gold stripe. The ad says “This Comet is now offered with refurbishment records, Vincent Owners Club Official Dating Certificate, and a transferable New Hampshire registration in the seller’s name.”
In the comments section, the seller says “I have owned Vincents for close to 30 years and been a member of VOC have worked in motorcycle industry since 1992, have had my motorcycles in major publications thru the years. I’m a master mechanic with a machinist back ground and restore motorcycles for myself in my shop at home part time now.” Sounds like it would be easy to check out their work and background, then, if you’re nervous about spending big bucks on a vintage Brit bike online.
That is the reality, after all—while this bike won’t get the same sell price as a Black Shadow, it will command a high hammer price. At time of writing, it’s bid up to almost $22,000 USD, and it will undoubtedly continue to rise. They aren’t making any more Vincents, and the Series C Comet production ended around 3,500 machines back in the mid-’50s. If you want a 1950s take on Supermono construction, you’re going to have to pay up.