Probably the greatest racing bike ever made, the Manx Norton won its first world championship round in 1949 (the Senior TT) and was still winning 20 years later, taking the Yugoslav GP in 1969. It wasn’t a one-off either; finishing third overall in the 500 world championship that year, ridden by Godfrey Nash.
The first Manx Nortons were offered as over-the-counter racers late in 1946, ready for the 1947 season. In those days they had a plunger frame, nick-named the ‘garden gate’, but this was replaced by the famous ‘featherbed’ swinging arm frame in 1950 for the works bikes and 1951 for customer bikes.
Available as 350cc or 500cc, Manx engines were each tested at the factory and guaranteed to produce 35bhp and 47bhp respectively. While these are good figures for a single cylinder four-stroke, even with overhead cams, many famous tuners worked their magic over the years, claiming over 50 and even over 60bhp for the 500 as the years went by.
Designer Joe Craig was once asked how he achieved such high power from a long-stroke single cylinder motor. He replied that he ‘was not proud’ of the high piston speed he had to use; engineers from rival companies thought the Manx simply should not work as well as it did!
So how fast was a Manx with all this power? In a speed record attempt in Australia in 1957 a 350 Manx averaged over 126mph and a 500 over 141mph. While probably not typical of a bike as purchased from the factory, these figures show what was possible with careful preparation.
Sidecar outfits based on Manx Nortons also dominated international racing during the 1950s, not least through the exploits of Eric Oliver who became a four-time world champion. Initially using the featherbed frame attached to a racing sidecar, the outfits later evolved into ‘kneelers’ using a more integrated design in which the rider knelt over the engine. Norton’s sidecar reign was finally ended by the works BMW flat twins.
Manx Norton engines even powered successful racing cars. Formula 500 (later called formula three) was for single seaters with 500cc engines and ran from 1948 to 1958. The Manx engine dominated the class, being used by many famous drivers including Stirling Moss and Jim Russell. Interestingly, BMW’s twins were completely outclassed by the Nortons in this category.
The famous Vanwall F1 cars used engines that were basically four Manx Nortons combined into a single assembly as a 2.0 litre, later enlarged to 2.5 litres, and even used four Amal motorcycle carburettors. Rated at 285bhp on alcohol fuel, the Vanwalls won the first ever F1 constructors championship in 1958.
After Manx Nortons were eclipsed by 2-stroke Yamahas in racing, they were rarely seen or heard in action until the ‘classic’ motorcycle movement took off in the early 80s. They have now become so popular that an entire cottage industry has developed, manufacturing everything from frames and fuel tanks to complete engines, giving the Manx a second lease of life and introducing it to a new generation of riders and spectators.
Have you seen one in action? Let us know in the comments below.