Velocette KSS
he Velocette KSS was in production from 1925 through the 1948 model year, interrupted, of course by 4 years of wartime production during World War 2. The “K” in the name indicates that this is an overhead cam (OHC) engine and the “SS” stands for ‘Super Sport’. The KSS was a 350 (actual displacement was 348cc) that made 19-25 hp (a lot for a 350 in those days) and was capable of an 80 mph top speed. It weighed just 265 lbs. So the Velocette KSS was a brilliant performer by the standards of the day. A modified KSS achieved 90 mph at the Isle of Man TT, although its excellent handling had something to do with that.
This 1946 Velocette KSS shows the rigid frame and girder forks used throughout its life. Despite these primitive accoutrement's, they had a reputation for great handling.
Velocette KSS Background & History
The Velocette KSS has the distinction of being the first bike to employ a positive-stop foot-operated gear change, which was attempted first on the race versions, then it filtered down to the roadsters. The KSS however was hand-shifted and had a 3-speed gearbox. The KSS Mk II came out in 1936 with an alloy cylinder head and shared its chassis with the Velocette MkV KTT. Velocette was ahead of its time with the K-series of engines. Typical of the day, they were air-cooled, vertical singles with grossly undersquared bore & stroke dimensions. However, most of its contemporaries used a block-mounted camshaft (or two) which operated their overhead valvegear. Velocette placed the cam over the top of the cylinder head (Overhead Cam or OHC) driving it with a shaft running up the right side of the engine, with bevel gears on both ends. It was the method of choice for driving far-away cams, back then, as small chains weren’t reliable enough yet. It provided a lot of power out of a fairly small package (although the engines grew quite tall), fairly reliable (by the standards of the day), and they loved to rev. A very successful design that was built, developed and perfected over 20+ years of production.
The "Cammie" engine had a bevel-shaft running up the side of the engine to power the overhead cam.
Velocette KSS Wins Races
Racing successes were many during its storied career. In 1926 Alec Bennett rode a Velocette KSS to victory at the Isle of Man Junior TT. The next year he placed second, again riding a KSS. In 1928 he returned and won the event. Velocette KSSs were always known for their great handling, even though they had a rigid frame for its entire production life. Up front was an ancient girder front fork right up until the end of production in 1948. However, starting in 1946, the Dotty Oleomatic telescopic forks, which were absolutely state-of-the-art at the time, were available as an option.
1946 Velocette KSS engine, primary drive side.
Velocette KSS Engine Design
The drawback of the Velocette KSS was that it’s “Cammie” engine took four times as long to assemble as one of Velocette’s pushrod bikes, like the MAC. This pushed the price of a KSS up higher than the other bikes, and although the OHC engine was very sexy, Velocette’s pushrod bikes, like the MAC, were just so darned good that the extra expense was hard to justify for most buyers. Because of this, the Velocette KSS was discontinued after the 1948 model year to concentrate fully on the company’s less complicated, and less expensive pushrod models. This greatly simply manufacturing for Velocette, since highly-skilled artisans were required to assemble an OHC KSS engine whereas workers of normal skill levels could assemble a MAC, for instance, and do so in far less time.
This 1946 Velocette KSS shows just what a handsome machine they were.
Velocette did well building high performance singles in the 1930s, but by the late 40s big singles were being eclipsed by a whole new crop of vertical twin. And Velocette, a small independent company not under the car of a big parent company like BSA or AMC, they never had the money to develop a vertical twin. In fact, other than Vincent, they're the only major classic British motorcycle manufacturer back then who didn't do a twin. And they were left behind as the result. Not only could the big singles not keep up with the twins on the street or track, they couldn't compete in the showroom either. Velocette didn't know it yet, but the handwriting was on the wall. I'm sure they believed that their singles were so good that people would buy them anyway, but times were a'changin' and Velocette never did what had to be done to stay in the race. By the 1960s Velocette wasn't just trying to keep up with it peers in Britain, now they had the Japanese to contend with and they never stood a chance. Velocette closed its doors in 1971.
Velocette KSS Motorcycle Books
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