Norton Manx
Norton Manx Background & History
The Norton Manx was one of THE premium road racing motorcycles throughout the late 1940s, through all of the 1950s and into the early 1960s. Norton has a rich tradition of road racing, having participated and won the inaugural Isle of Man TT in 1907, and participated in every Isle of Man TT event well into the 1970s. No other manufacturer can make that claim, or anything close to it. Norton’s first use of the ‘Manx’ name was applied to a special race version of their popular single-cylinder Norton International street bike from 1936 through 1940. The big 500 got all the latest, greatest race equipment: magnesium engine cases and rocker boxes, telescopic forks (a new thing at the time) and Norton’s latest ‘garden gate’ frame, with plunger rear suspension. The 1936-40 Norton Manx Grand Prix, as it was named, and did well in pre-War competitions.
This 1948 Norton Manx shows the old Garden Gate frame with plunger rear suspension. This was the last year before the Featherbed Frame arrived.
When civilian production resumed in 1946, following World War 2, Norton was back at it, and created yet another Manx model in 1947. Again spun off of the Norton International, this Manx had a newly-designed overhead cam (OHC) head, available in 350cc and 500cc displacements. Again, it used the ‘garden gate’ frame with plunger rear suspension. Swing arms hadn’t arrived in England yet.
Note how the Featherbed Frame is built. Each of the main frame rails is formed by a single piece of tubing. It starts and stops at the steering head (neck). Check out how the down tubes attach to the top of the neck and the backbone attaches to the bottom, and they cross, for greater strength.
Norton Manx Debuts the Featherbed Frame
Joe Craig was in charge of all of Norton’s factory race bikes in those days, and fielded many experimental models. In 1949, he contracted the McCandless brothers to design an all new frame featuring a rear swing arm suspension. What they came up with is something that became known as “The Featherbed Frame”. At a time when most bikes had rigid frames (no rear suspension), the swing arm with two vertical shock absorbers was unique and very advanced for the times. Most other frames were formed by brazing the ends of the frame tubes into heavy cast iron lugs. It was heavy, clunky-looking (steam-era tech) and not very rigid. The new Featherbed Frame was formed mainly from two 20-foot lengths of Reynolds high strength steel tubing that were bent in one unbroken length into the shape of each side of the frame. Each tube starts at the steering head, then heads down and around the engine, it curves gently upward and forms the backbone of the frame. The whole thing was welded together, no lugs. It was thoroughly modern, and it changed the way people designed motorcycle frames from then on. The net effect of all this was a very light, strong, rigid frame with the excellent rear swing arm suspension. The two main weak points on any such frame are the steering head (neck) and the swing arm pivot, so these were duly reinforced to be incredibly strong. And a frame geometry was dialed in that endowed the Featherbed with otherworldly handling when compared to other bikes of the day.
This 1959 Norton Manx shows how the Featherbed Frame looks, starting in 1949.
Launch of the Norton Manx
In the meantime, Norton had released the new post-war Norton Manx as a 1947 model with the best frame they had at the time: the archaic Garden Gate frame. Late in 1949 prototypes of the Norton Manx built on the Featherbed Frame were doing track time and by 1950 the bike was released to the public as a full production model. It completely transformed the bike. Instantly the Norton Manx became unbeatable. The power and torque produced by the big DOHC single couple with the Featherbed were unstoppable. On the new bikes’ first time out, two podium positions were won by a Norton Manx at the 1950 Isle of Man TT.
Norton Manx Engine
The Norton Manx engine was available in 350cc and 500cc. They were all dual-overhead cam engines, built for different events and with different states of tune. At the top end, the 500 made as much as 47 hp at 6,500 rpm. Those rpm are even more impressive when you consider how undersquare the engine was. The 500 had a bore of 79.62mm and a stroke of a whopping 100mm. That’s a long way for that piston to travel, especially at 6,500 rpm. So, in 1953, the 500cc Norton Manx engine was redesigned to bring it more in line with modern thinking, ie: oversquare engines are better. The new engine was actually almost square (bore equals stroke), but still slightly oversquare at an 86.1mm bore and an 85.6mm stroke, with the goal of allowing it to rev higher. It worked, the new engine produced 54hp at 7.200 rpm and was good for 130 mph.
1959 Norton Manx engine. Note the heavy finning for cooling, the magneto behind the cylinder and the long intake manifold tract aimed straight at the intake valve.
Norton Manx Nears the End of the Road
Norton withdrew from International Grand Prix Racing in 1954 but continued to supply privateers with the race-ready Norton Manx, and privately-owned Manxes ruled many GP events in Europe and England well into the 1960s. The last Norton Manx rolled off of the Bracebridge Street factory, the original home of Norton production, in 1963. Like the BSA Gold Star, another legendary big British single, it was a victim of the times. The advance of the vertical twin certainly hurt, but by the 1960s, cheap, high-quality Japanese bikes began flooding the market and it was game over for big 4-stroke singles. Besides, Lucas Electrics was discontinuing production of the magneto that nearly every motorcycle in Britain used to make spark, including the BSA Gold Star and the Norton Manx.
Today, companies all over the world are producing brand new reproduction Manx Nortons (Norton Manx and Manx Norton are used interchangeably) to various specifications, equipment and states of tune. Most qualify to compete in Classic Motorcycle Racing and History Motorcycle Racing around the world.
The Norton Manx engine is a thing of beauty. This one, lightened for racing, replaces the primary chain case with a simple chain guard, exposing it's lightened clutch. Very cool.
Norton Manx Books
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