Another route to a ‘four’ was to stuff a small car engine into a motorcycle frame; that was the route of Friedl Münch, who series produced his ‘Mammut’ – see our test ride here. The most capacious frame in the 1960s was the Norton Featherbed, which had been in production since 1952, meaning plenty of ‘loose’ frames were available in salvage yards by the 1960s. A four-cylinder car engine with the right ‘spec’ was hard to find, as most automotive ‘fours’ were both water-cooled and made of cast iron – guaranteeing a very heavy motorcycle. A few small engines were of more advanced spec, and the two most likely candidates (in Europe at least) had deep motorcycle connections built into their DNA.
The Hillman ‘Imp’ had a powerful watercooled engine, designed by the unsung Norton hero Leo Kusmicki, the man who touched the ‘Manx’ with his magic wand and kept it competitive for 10 years after its ‘sell-by’ date. Kusmicki worked for the automotive industry after Norton shuttered its race shop, and the overhead-camshaft ‘Imp’ engine he designed was strong and tunable. Its water cooling dissuaded many solo motorcyclists, although plenty of racing sidecar outfits found the need to carry water a small price to pay, given the cheap power an Imp provided. Who needed the money of Count Agusta when a wrecked Hillman provided a readymade power unit?
Another likely donor came from venerable motorcycle manufacturer NSU. The engine from their ‘Prinz’ automobile, which served long years as a rally competitor, was tuned over the years to ever sportier iterations, with the ‘1200 TTS’ the ultimate mode. The NSU engine was air-cooled and all-aluminum, with handsome finning, and few awkward casting shapes to spoil its looks. The Prinz engine fit into the Norton frame without cutting metal, although a new bolt-on sump needed to be designed to fit a Norton frame. It looked simple, but the reality of mating the NSU engine with a motorcycle gearbox, plus sorting a primary chain, and clutch, and a functioning oil sump, required skilled fabrication. Everything needed to line up and function smoothly, and only a talented stylist could make the result look like a proper motorcycle.
Mick King, owner of Superformance Motorcycles in Vancouver (one of the first performance/custom bike shops in Western Canada) built an interesting special in the late 1960s, using a Norton Featherbed frame and a salvaged NSU car engine. Mick was kind enough to share his process, in photos, of taking a rustbucket NSU Prinz and a 1967 Norton Atlas chassis, to build a successful hybrid. The photos hint at the measuring, drawing, and fabrication time required to bring the elements together; the magic of a successful job is making it easy! The Italians call this ‘Sprezzatura’ – making the difficult look effortless; the mark of mastery. Mick’s build took long enough that both the Honda ‘CB750’ and the Norton ‘Commando’ emerged on the market in the meantime, but as his machine was never meant as a production exercise, the Commando contributed useful bits to his Norton/NSU: the front forks and disc brake, mufflers, seat, and clutch.
“In the 1960s, there were no NSU dealers in Vancouver, and the car owners couldn’t get them repaired… I had a motorcycle shop, and would fix a few NSU cars because I had managed an NSU dealership in the UK. They were so simple to work on, it was a good revenue source and sideline to my motorcycle business, which was one of the first on BCs west coast. I took in a trade an NSU 1200 TT car for two hundred bucks; due to rat infestation and rust the car was gutted and the wheels and sundry items sold off. I kept looking at the engine thinking it might look good in one of my Norton Featherbed frames, which owed me nothing… I had a couple gathering dust in the attic!”
“As winter started in, the bike work stopped; I had just brought over an apprentice from the UK, and a new 9-1/2” South Bend lathe for our custom bike division, and decided to see if we could fit the NSU motor into the Norton frame. This gave the new arrival some valuable turning experience. We wanted the engine to fit the existing Norton engine mounts, as I did not want to mess up the frame for the sake of the NSU engine; I had no input or feedback as to how it may perform. When the Münch showed up in Cycle Canada magazine I thought, “Great timing! Maybe I can find some encouragement from the article!” But there was no data -no speed or bhp- as I recollect, the mag people were not allowed to ride it? So we plodded on, and after a few weeks the engine was roughed-in, and we took it for a ride. I could see why there was no data available – it was a gutless wonder, despite major engine work! I considered buying a twin-cam Japanese car engine but they were all snapped up for mini flat track race cars, as they are today!”
“Trying to draw a comparison with the Münch would be a waste of time in my opinion, considering the amount of money he invested, plus his engineering facilities and so on. Nevertheless I think from the get-go the Münch Mammut was doomed, mainly because D.O.H.C. motorcycle engines [such as Kawasaki Z-1] were already making their debut, and strapping an antiquated and gutless S.O.H.C NSU car engine into such an enormous and costly project baffled me and my mechanics from the get go. Then there was the price… ridiculous!”
The two ‘big’ jobs in translating the engine from car to bike were the sump, which Mick cast in shapely aluminum to fit between the Norton frame rails, and the clutch/transmission interface, which he solved via an extended, demountable coupling between the gearbox and clutch, using a ‘simple’ steel box attached to the engine plates, which holds an outrigger bearing for the extended clutch shaft. This also meant installing the Norton gearbox backwards! Yes, it works fine both ways, but Mick had to reverse the ‘pawl’ on the kickstart shaft. The photographs should explain his thinking, which seems sound enough – the clutch no longer runs on the gearbox mainshaft but its own stub shaft, connected to the gearbox via a mated pair of pegged plates, similar to BMW shaft-drive practice. All very clever and relatively simple.
The donor NSU model was the ‘Prinz 1000’, and had Mick King read the specifications for this model, he might have thought twice about the engine! While an impressive ‘spec’ the standard Prinz only produced 40hp @ 5500rpm, which is about 10hp less than the Norton Atlas engine which he abandoned to make his ‘special’… no wonder then that he was shocked to find his finished hybrid a ‘gutless wonder’. If Mick had access to the latest model (1968) NSU TTS, he would have found a 70hp engine, using 10.5:1 compression pistons (not much room for increase there!) and sporting camshaft. But Mick set to work tuning his the motor, and his Norton/NSU was capable of 125mph, so it seems he equaled the NSU factory in hotting up the engine.
The finished machine did well on the ‘show bike’ circuit in the early 1970s, garnering Mick many ‘Best of Show’ wins, and that snapshot with the 1973 Penthouse Pet of the Year, Patricia Barrett. Mick’s Norton/NSU special now lives in the Trev Deeley Museum in Vancouver, Canada.