Norton Manx F-Type replica in the studio

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Norton Manx F-Type replica in the studio

Picture book work

Content of

As a template for this replica of a lost Manx prototype, Franz Schleifer only had a few photos to hand. The gifted craftsman has built the Norton racing machine with great skill – without a single design drawing!

E.t was in the mid-1980s when Franz Schleifer came across a little book that was to become very important in his life while visiting England. Because the Norton lover and Manx owner discovered a machine in it that impressed him so much with its line that he really wanted it.

Norton Manx F-Type replica in the studio

Picture book work

Norton Manx F-Type – the F stands for "Flat" and thus the horizontal cylinder – never got beyond the prototype stage. The F-Type was a secret project by a handful of people in Norton’s racing department. Intended as an answer to the victorious Moto Guzzi racers who had wrested the world championship crown in the 350s from the Norton works team in 1953 with just such a lying single-cylinder. But before the promising F-Type could be used, Norton announced the withdrawal of the works team from GP racing at the end of 1954.

Only engine fragments remained of the F-Type prototypes

Of the F-Type prototypes – apart from the 350 series, a 500 series version was also built – there were only engine fragments that were "rescued" by employees of the racing department. And they had no interest in giving out information or parts of it. “Since there is nothing to buy, I just have to build the F-Type myself.” Schleifer’s insight, which is as simple as it is presumptuous, is put into perspective when you know that he is known in the scene as “Norton-Franz”. Not only because he was “still loyal to the Manx as an ID racing driver when the two-stroke engine had long since dominated”. But also because he masters the mechanically extremely complex Manx engine like crazy. 

The trained engine fitter and experienced precision mechanic got to work in 1989, building the first engine with defective Manx parts that were already on the shelf. These were repaired and adjusted. "Of course I had doubts whether I could really do it myself," he admits, "but I just had to try it."

“I have my ideas and concepts in my head"

And without a single construction drawing, because there wasn’t one. “I have my ideas and concepts in my head. That’s enough if you know what you’re doing. ”Words from a practitioner who probably make their hair stand on end when studying engineers. But it only took about a year for Franz to push his first “prototype”Out of the basement workshop at home. As in the original with the cylinder and head of the stationary engine. It was of course clear to him that the ribs were not suitable for the horizontal arrangement. Nevertheless, it worked for some function tests, whereby the engine initially “ran more badly than right”. Typical of a test vehicle, which also only came closer to the model in the photos in many details such as wheels, brakes or seat humps over the years. Then, in 2010, there was a big bang on the Salzburgring. Thermal overload in combination with problems in the oil circuit led to the piston jamming with a connecting rod torn off and a broken motor housing.

Not an unusual fate for a prototype, the Norton factory team would probably have had to put up with such setbacks if the project hadn’t been stopped so suddenly. Which is why Franz did not throw the gun in the grain. The new Manx motor housing tore a big hole in the household budget, but gave the impetus to “do everything right now”. Whereby correct mainly meant an adapted ribbing for the lying arrangement. And thus, among other things, the in-house production of cylinders and heads.

Everything about Norton motorcycles

Secondary chain drives the rear wheel

Only in one point was it certain from the outset that an exact replica would not be possible: The factory F-Type had a unit motor with an integrated gearbox, the primary drive of which required a crankshaft rotating "backwards" via two gear wheels. Too much effort, decided Franz – and built his own solution with the five-speed gearbox of the Manx in the adapted housing. This is why the secondary chain on his Norton Manx F-Type replica drives the rear wheel on the left-hand side, on the original it is exactly the other way around.

Otherwise, however, the 71-year-old has kept the Norton Manx F-Type replica very closely to the model shown in the photos. Of course, this also applies to the striking central tube frame with a diameter of 110 millimeters, which also stores the oil. Franz made it himself from precision steel tubing with a wall thickness of 1.5 millimeters and brazed connections, as well as the mounting of the two-arm swing arm with oval tube cross-sections, made from solid aluminum profiles. The aluminum triple clamps and the brakes are also made in-house by the handicraft artist, with the ventilated anchor plate and the self-made fan disc at the front of the double-cam duplex brake particularly striking for better heat dissipation like the original.

No fuel pump necessary

At the rear he also came up with a specialty: the rear wheel hub is based on the factory racing motorcycles, with a chainring that is separate from the brake hub. This enables a free choice of gear ratio and prevents the hub from overheating due to friction. So it is hardly surprising that the Swabian, who was born in Austria, also welded the elegantly shaped tank from 1.5 millimeter thick aluminum sheets himself. However, it looks much bigger than it actually is, because the voluminous container of the Norton Manx F-Type replica does not hold more than ten liters of fuel. By the way, because the builder subdivided it in such a way that the fuel in the upper area reaches the carburettor according to the downdraft principle, which is why – unlike the original – no petrol pump is required here.

This already shows that Franz Schleifer did not set up his Norton Manx F-Type replica as a mere showpiece. Now, with the adapted ribbing, thermal problems are no longer an issue. The revised oil circuit and an additional oil sump tank under the crankcase also increased reliability. The "Norton crazy", as Franz Schleifer calls himself, can now fully enjoy his F-Type replica, which he presented to an enthusiastic audience with the new engine three years ago, at his rare public appearances. It’s a mutual pleasure. With his self-construction, which is spectacular in every respect, Franz has shown that it sometimes only takes a few photos to deliver a picture-book work.

Construction of the second engine

Bilski

Here you can see the self-made molds for the cylinder head.

Lay flat

From the beginning it was clear that a unit engine like the one in the original was out of the question – the effort and costs for the molds for a block engine would have been far too expensive. Franz decided to take the parts of an ordinary Norton Manx except for the cylinder and head and combine them with its AMC five-speed transmission. However, this made it necessary to shorten the crankcase in order to keep the wheelbase as compact as possible despite the horizontal cylinder. Franz separated 60 millimeters from the Manx crankcase in the area of ​​the oil sump and closed it with a lid. However, there was no longer any space for the standard crankshaft, which was therefore turned off by 30 millimeters on the lifting discs and rebalanced. The stroke of the standard 500 Manx piston (86 mm) is now 76.6 millimeters, as with the 350. Schleifer worked the cylinder with the horizontal cooling fins from solid pieces.

But the greatest adventure was the cylinder head. Since professional model builders called up priceless sums for a casting mold, Franz got down to work himself. Using the photos, he made a drawing for the dimensions, number of ribs and their position and, with the help of a model maker friend, built the three required molds. To the surprise of the two, the first casting was successful. Since this was done without cores, Franz had to mill the channels and valve seats from solid. The head (valves, springs, bevel shaft and gear cascade including the two camshafts) was then fitted with original Manx parts.

Technical specifications

Bilski

There were no construction drawings. Franz Schleifer had his ideas and concepts in mind.

Norton F-Type replica 

Engine: Air-cooled single-cylinder four-stroke engine, arranged horizontally, two valves, bore 86 mm, stroke 76.6 mm, approx. 440 cm³, approx. 45 hp, a 35 Amal GP carburetor, multi-disc dry clutch, five-speed gearbox, chain drive

Landing gear: Central tubular frame, Ø 110 mm, with integrated oil tank, Norton Roadholder fork at the front, two-arm swing arm at the rear, duplex drum brakes at the front and rear, dry weight 132 kg, tank capacity approx. 10 l, tires: 3.00-19 front and 3.50-19 rear

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