Norton's association with the Isle of Man TT defined the company's racing identity for more than six decades. The name "Manx" was first applied in 1936 to a special racing version of Norton's International roadster, available until 1940. After World War II, Norton relaunched the model simply as the Manx in 1947. It was a lightly redesigned descendant of the prewar racing International, available as a 350 cc or 500 cc overhead cam single-cylinder machine. Development was led by Norton racing team engineer Joe Craig, who had spent decades coaxing performance and reliability from single-cylinder camshaft racers.
The Manx's double overhead cam configuration was developed as early as 1937, refined through 1938, and was ready to re-emerge for the 1946 Manx Grand Prix following the wartime interruption. Early upgrades added telescopic forks, and twin leading shoe brakes arrived in 1948.
The defining transformation came in 1950 with the adoption of the Featherbed frame, designed by the McCandless brothers. The all-welded tubular frame was notably light, free of unnecessary forgings, and gave the Manx a low centre of gravity and short wheelbase ideally suited to the demanding TT course. In the same year the featherbed Manx recorded a double hat-trick of podium positions at the TT. In 1953 the engine was redesigned with a much shorter stroke — 86.0 mm × 85.6 mm — to extend the rev range and improve power delivery.
A significant further upgrade was planned for 1954: a horizontally mounted cylinder to lower the centre of gravity further, in the manner of the Moto Guzzi and Benelli racers. However, declining sales prompted multiple manufacturers, including Norton, to withdraw from Grand Prix racing that year. The unbuilt F Type Manx prototype survives and is displayed in the Sammy Miller Museum Collection. With the factory's withdrawal, Joe Craig retired after more than 25 years of development work.
Despite Norton's withdrawal from works Grand Prix competition in 1954, the Manx remained the backbone of privateer motorcycle racing through the late 1950s and 1960s. The motorcycle also recorded wins at the Bol d'Or endurance race from 1958 to 1971.
The final chapter of the Manx's factory-era racing career came in 1969 when Godfrey Nash rode a Norton Manx to victory at the Yugoslavian Grand Prix at the Opatija Circuit — the last time a 500 cc Grand Prix race was won on a single-cylinder machine.
Factory production ended after 1962. In July of that year AMC announced the transfer of Norton production from Bracebridge Street in Birmingham to Woolwich in London, and 42 final Manx Nortons were built between November 1962 and January 1963.
British racer Les Archer Jr., working with frame specialist Ron Hankins and engine tuner Ray Petty, adapted the Norton Manx for motocross competition. The double overhead cam, short-stroke road racing engine was fitted into a Hankins frame and finished with an aluminium tank and titanium axles. The resulting machine won the 1956 FIM 500 cc European Motocross Championship. A later 1962 version could not, however, compete with the emerging two-stroke bikes that dominated the mid-1960s.
The Manx Norton also played an unexpected role in the development of post-war car racing. When English national 500 cc regulations were adopted as Formula 3 at the end of 1950, the JAP Speedway engine had initially dominated the class. The Manx produced significantly more power than the JAP and became the engine of choice for Formula 3 cars. Many complete motorcycles were purchased solely to strip out their engines, since Norton would not sell engines separately.
After Norton ceased Manx production, Colin Seeley purchased remaining spares and tools in 1966, later selling them to John Tickle in 1969. Tickle continued manufacturing under the Manx name, producing the T5 (500 cc) and T3 (350 cc) models using short-stroke Manx engines in a frame of his own design, before selling the rights to Unity Equipe in the late 1970s.
Manufacturing rights passed to Bernie Allen in 1989, who produced a limited run of machines in 1992 and 1993 under the Allen Norton name. Andy Molnar acquired the rights in 1994 and produced parts, engines, and complete machines faithful to the original 1961 drawings, marketed as the Molnar Manx. A road-going version, the Tonkin Tornado, developed with ex-racer Steve Tonkin, was available into the 2010s.
The Classic Motorcycle Racing movement from the 1970s onwards sustained demand for the Manx, and a global network of parts suppliers and restorers continues to service the large number of machines that return to historic racing circuits around the world. New Manx Nortons built to various specifications remain available from several independent suppliers.