1972 Fastback

Norton Commando Fastback

Vibration was always the curse of big British twins but Ian Falloon admires Norton’s innovative solution…

In 1967 England was on a high. It led the world in music and fashion, and was at the forefront of engineering innovation. This was the time of the Beatles, Rolling Stones, miniskirts and the Harrier vertical take-off jet. But England’s previously dominant motorcycle industry was in decline. Edward Turner introduced the Triumph Speed Twin in 1937 and not much changes over the following 30 years. Norton followed Triumph with its 500cc Model 7, gradually enlarging it to 600cc, 650cc, 750cc, and eventually 850cc. As it grew, so did the vibration, culminating in the 750cc Norton Atlas; the greatest vibrator of all.

There was little Norton could do about the vibration of their long-stroke twin. Large capacity parallel twins, especially the 360-degree type like the Norton with both pistons rising and falling together, vibrate extraordinarily, but in a single plane. Lacking the resources to completely design and retool for an all-new engine, Norton created the ingenious Isolastic system. The engine, gearbox and swingarm were rigidly mounted together in one unit and coupled to the frame through rubber mounts. These only allowed movement in a single plane, effectively isolating vibration from the rider without compromising handling. At the same time the engine’s cylinders were inclined forward, getting away from the old-fashioned look that harked back to the Norton singles. While it may have looked newer, the design was still rooted in the past. Valve operation was by pushrods and rockers and there was a separate four-speed gearbox, joined together by a triplex primary drive chain. Oil leaks were part of the package.

The frame was also completely different to the earlier Featherbed type. Norton had engaged Austrian-born Dr Stefan Bauer as director of engineering and Bauer dismissed the iconic Featherbed frame as “rubbish”. Bauer preferred a spine-type frame and specified one built around a large, 57mm backbone tube. When the Commando was first released, purists were aghast that Norton had abandoned the Featherbed and there was much scepticism as to how the Commando would handle. One ride was enough to prove all the detractors wrong. The Commando’s handling was well up to traditional Norton standards and, with the engine vibration isolated from the rider, the Commando could be ridden harder for longer. The engine may have been shaking itself to pieces, loosening carburettor float bowls and exhaust header pipes, but the rider was quite oblivious to all this activity.

In its transition from Atlas to Commando, the 73 x 89mm 745cc twin’s compression ratio went up to 8.9:1 (from 7.6:1) and the carburettors to 30mm Amal concentric. The power increased from 49 horsepower to 56 horsepower at 6500rpm. While the gearbox was largely unchanged, the Commando received a four-plate, diaphragm spring clutch. This allowed double the plate pressure without any noticeable increase in hand pressure. The power wasn’t startling but the complete Commando weighed only 181kg and the 19-inch wheels rolled on a very moderate 1441mm wheelbase. The suspension was also top quality: a tried and trusted Norton Roadholder fork and Girling shock absorbers.

For 1968, just prior to the big-bore Japanese onslaught, the Norton Commando’s performance was sensational. The top speed was over 190 km/h and the Commando could cover the standing 400 metres in a little over 13 seconds. The Commando was an instant hit, remaining popular even after the Japanese 750s arrived, winning the British Motor Cycle News “Machine of the Year” poll for five years in a row.

After 1971, Norton was seduced into the horsepower war, boosting the power of the 750 to 65 horsepower. This engine, known as the Combat, was only an option on the Commando for 1972 but its 10:1 compression ratio and voracity for high revs was too much for the main bearings. Almost every Combat engine quickly failed and Norton was forced to dismantle an entire assembly line to fit improved components. It was an expensive mistake  and one from which the company struggled to recover.

Norton’s nomenclature had risen to the Mark IV by 1972 and along with the Combat engine came a Lockheed front disc brake. Nearly all Mark IV Combats were Roadsters or Interstates but the traditional Fastback was still available in small numbers. Phil De Gruchy spotted one in the Peter Stevens showroom in Elizabeth Street, Melbourne, in September, 1975.

“It had been brought out from the UK by the original owner and had only 3000 miles on the clock,” recounts Phil. “The price was $1175, a bargain compared with the $1995 asked for an 850 at the time.”

Phil stopped riding the Fastback in 1983 with 45,000 miles on the clock but, in 2011, began a total refurbishment. Apart from the Borrani rims, the bike is very stock right down to the fibreglass tank and seat unit, both in original red gelcoat. And it is still a bike that can be ridden regularly as Phil can attest.  His refurbished Commando is a regular at Classic bike events and club runs.

Although ubiquitous and arguably always obsolete, the Commando Fastback possessed all the endearing qualities of a classic British motorcycle: a torquey twin cylinder engine, moderate weight, excellent handling and, above all, timeless looks.

Many thanks to Phil De Gruchy of Lightfoot Engineering, Mont Albert, Vic, for the use of the Norton Commando Mark IV Combat Fastback featured.

 

Five commanding things about the Norton Commando Fastback

The first Commando of 1968 was a fastback, but was known as the 20M3. The styling was by David Bristow, in charge of 3D design at Wolff Olins, a London design agency.

The Norton Commando was the first motorcycle to be launched with corporate branding. Wolff Olins dreamed up the trademark “green blob” that appeared on the fuel tank of the prototype. These green emblems were derided and only appeared on the prototype.

During 1969 the first Commando was renamed the Fastback. There were subsequently four Fastback versions, the last  being the Mark IV of 1972. The Fastback continued to feature a fibreglass fuel tank, although Italian-made steel tanks were available as an option.

As the standard Fastback only had a 15-litre fuel tank, a Fastback LR (Long Range) was introduced in 1971. This had a larger (18-litre) steel tank and a revised seat. Only around 400 Long Range Fastbacks were produced.

The 1972 Mk IV Fastback was unique as it was the only Fastback with a front disc brake. All other Fastbacks had a front drum brake.

Note 1: Bauer dismissed the iconic Featherbed frame as “rubbish”.
Note 2: The top speed was over 190 km/h and the Commando could cover the standing 400 metres in a little over 13 seconds.

Words & Images: Ian Falloon