With an experienced team and a lot of data.
Protect your 1957 Velocette Viper from the unexpected.
Velocette was a small motorcycle manufacturer based in Birmingham from 1905-71, and was long known for the quality of its racing bikes, especially from the 1920s through the 1960s. After starting with modestly successful 250 cc two-strokes in 1913, the company developed its first overhead camshaft four-stroke single in 1925. The “K” series was refined into the competitive KTT, which remained competitive in British racing, and at the Isle of Man TT from 1928-49.
The OHV 350 cc MAC was introduced in 1933, followed by the 500 cc MSS in 1935. The 350 cc MAC powered Velocette’s WWII army bikes, but after the war the company began a 20-year diversion with a pressed-steel frame Neracar-like scooter called the “LE” (for little engine). Powered by a water-cooled 150 cc (then 192 cc) horizontal twin, it was slow but indestructible, and favored by police patrolmen.
Meanwhile, the 349 cc MAC won the 350 cc World Championship in 1950, and evolved into the 350 cc Viper and 500 cc Venom in 1956. Velocette still flirted with horizontal twins, with the 200 cc Valiant and bizarre Viceroy fiberglass scooter, but the excellent Viper and Venom saw the company through to its demise in 1971.
The single cylinder 350 cc Viper was developed from the MAC and introduced in 1955. It was fitted with a high-compression piston and alloy cylinder head and shared its bottom end with the 500 cc Venom, which was designed to compete with the new range of British twins. Desert racing versions of both models were launched in the U.S. in 1956. Clubman models bowed in 1960, fitted with Amal TT carburetor, racing magneto, clip-on bars, rear sets and tachometer. A 500 cc Venom was the first bike to record 100 mph for 24 hours at Montlhery race track in 1961.
The Viper and Venom both had some unusual characteristics. Velocette’s rear swing-arm was more complicated than other manufacturers and could be temperamental, but worked better when it was set up correctly. The clutch was located between the engine and gearbox, which made it easy to change gears for racing, but harder to work on the clutch, whose adjustment is something of a skill. Miller electrics were replaced by Lucas in 1962, and this was actually an improvement.
Velocette offered a high-performance cylinder head for the Venom in 1965, and a bike so equipped won the 800-mile Thruxton road race – hence the name of the subsequent model. Velocette claimed 41 bhp for the Thruxton with a top speed of 110 mph. It was fitted with a close-ratio gearbox and alloy rims, and the high-compression cylinder head was fitted with big valves and polished ports. The Amal 5GP carburetor was so big that the gas tank had to be cut out to accommodate it.
A Thruxton won the first 500 cc Production TT at the Isle of Man in 1967. It was never an easy road bike to live with, but the model had unmistakable cachet, especially with Velocette’s signature “fishtail” silencer. The model was aimed endurance road racing, in which bikes have to be production-based, and only 1,108 were built before the company’s demise. Many of the 5,721 Venoms built have been upgraded to Thruxton appearance, so it’s very important to check numbers before parting with hard-earned money.