Norton Commando 750 history
Norton is one of the great names in motorcycle racing, with its first historic TT win in 1907 setting a theme that was to continue throughout Norton's history. Norton built its reputation as a successful racer on the single cylinder engine, notably the 3350 and 500cc models, but finally moved to a parallel twin following World War II. Triumph set the trend in 1937 launching a parallel twin as the Triumph 'speed Twin', and Norton followed in 1947 with the 500cc Model 7 Dominator, and the Model 88 Featherbed Dominator in 1953.
The Model 7 Twin was a muscular machine and early production was reserved for export sales, with British customers having to wait until late 1949 to take delivery of the first production Norton twin in nearly 40 years.
Origins of the Norton Commando
The origins of the Norton Commando are found in the Model 7, with the twin cylinder design evolving into the 650cc Norton Dominator and 750cc Norton Atlas before being launched as the 750cc Commando in 1967.
The Norton Atlas was the starting point for the range of 750cc Norton twins that remained in production until 1975 and sold in many thousands all over the world. It became renowned for two things: its wide band of power and the vibration that accompanied enthusiastic use of its upper rev range!
The boost in size was achieved simply by increasing the bore of the 650cc engine from 68 to 73mm, with the stroke remaining at 89mm. The result was a bike with the ability to pull from 40 to 177km/h in top gear. This was further enhanced by the excellent featherbed frame, which provided good road holding. The vibration is said to have been a "design feature", with the vibration at high engine speeds encouraging use of the engine's flexibility. Whether there was any truth to it, we will probably never know.
The Norton Commando 750
Just as Norton had been taken over by AMC in 1953 and become a stablemate with the AJS and Matchless brands, it survived when AMC in turn folded and was acquired by Manganese Bronze Holdings in 1966. The group was named Norton-Villiers (having acquired Villiers Engineering), with the only two marques to continue production being the AJS moto-cross models and the Norton twins.
To ensure a future for the brand the new management recognised that the Norton twin needed considerable development to succeed. A team consisting of Bernard Hooper (responsible for the successful Villiers 250 Starmaker), engineer Bob Trigg and Dr Stefan Bauer from Rolls Royce was appointed to oversee development and design. Initially they looked at resurrecting the 800cc overhead camshaft that had been briefly used in the P10, but finally settled on the 745cc of the Atlas.
Hooper initially came up with a solution to the vibration problem, with the engine, gearbox and swinging arm all isolated from the main chassis by rubber-bushed mounting at the front of the crankcase, cylinder head and gearbox cradle.
While the system worked well, the bushes had a short life (around 8,000km) and road holding thereafter rapidly deteriorated.
This frame was to set the Commando apart compared to previous Norton models, eliminating the vibration problems. It was called by the rather grand name of the Isolastic anti-vibration system. While working well, it needed constant adjustment, which never endeared the system to owners or mechanics.
The 750cc Commando was launched at the 1967 Earls Court Show, finished in silver with a distinctive orange seat. It went into production in 1968 and was an immediate hit, being voted 'Machine of the Year' for five consecutive years by Motor Cycle News readers.
Initially the Commando had frame problems, breaking at the steering head, but this was rectified with a gusseted version frame introduced in January 1969. It was originally called the 'Fastback' and was joined by the production racers 's Type', which had a higher exhaust and a smaller 2.5 gallon fuel tank.
The engine was an air-cooled inclined parallel twin, with two pushrod-operated valves per cylinder, a compression ratio of 8.9:1, Lucas capacity ignition and twin carburettors. A handsome alloy primary chaincase housed the triplex chain-drive to a diaphragm clutch especially developed by Laycock Engineering. The uprated 745cc engine breathed more efficiently through twin Amal concentric carburettors, tilted forward in an aggressive angle that was echoed by the down tubes of the main cradle and the rear suspension units. A 14.7-litre tank was gripped by extensions of the dual seat side panels in the style of old fashioned knee grips.
The upper frame was a single 57mm (2.25-inch), 16-gauge tube with a duplex cradle sweeping elegantly around a triangulated rear section. Roadholder forks and the 203mm drum brakes came directly from the Atlas.
Spoked, steel rims were fitted with 19-inch tyres -- 3-inch in the front and 3.5-inch in the rear. Power was rated at 56bhp at 6500rpm, with a claimed maximum speed of 185km/h and a standing 402 metres of 13.5 seconds. Standard livery was a red tank and rear guard, with chrome headlight, front mudguard, lower forks, wheels and exhaust.
The sporting appeal of the Commando 750 was obvious and a special production TT model was prepared and ridden to second place in the 1969 TT behind the record breaking Triumph Bonneville of Malcolm Uphill.
May 1970 saw the appearance of the updated 's' Roadster, which featured a low mounted exhaust and upward angled silencers with reverse cones. In September the classic Fastback Mk2 was introduced with alloy levers and modified chain guards. The Street Scrambler and the Hi Rider were other variants on the basic Commando launched in 1971, along with the Fastback Long Range with an increased petrol tank capacity.
In 1971, a Formula 750 racing Commando appeared and was ridden to third place in the Isle of Man TT - a sad result considering Peter Williams' bike was comfortably leading until its ignition failed. Numerous Commando 750s were raced round the world with various levels of success.
The Combat engine was introduced in January 1972 and despite delivering 48kW of power at 6500 rpm with a 10:1 compression ratio, it was plagued with mechanical reliability issues, including main bearing failure and broken pistons. At the time the company was receiving Export Credit Guarantee payments from the British Government, and was less interested in solving the problem, merely exporting their problems instead! Eventually the fragility of the engine was cured with detuning and fitment of a high tolerance superblend main bearing that could tolerate the whip in the hard working crankshaft. Due to the Combat engine, the company received much negative publicity and undermined the generally good name of Norton. The year 1972 also saw the introduction of a disc front brake, along with updated models in the Mk4 Fastback, Roadster and the 750 Interstate.
Outside the control of Norton, by mid-1972 the BSA-Triumph Group were in serious financial trouble and the UK Government agreed to bail them out, conditional upon them merging with Norton Villiers. Norton Villiers Triumph was duly formed with Triumph proving to be a poor bedmate as the new group headed towards bigger problems.
The last of the Norton 750 Series, the mark V was produced from November 1972 to mid-1973 and featured improved reliability, with new crank bearings, camshaft and a reduced compression ratio. One final fling for the 750 saw a special Commando 750 produced to UK Police specifications. Named the 'Interpol' it sold well at home and abroad. It was equipped with panniers, top box, and fairing and had fittings for radio and other equipment. Reliability remained an issue with head gaskets blowing, exhaust pipes snapping and slipping clutches, along with swinging arm spindles wearing badly.
Significance of the Norton Commando 750
The Norton Commando 750 was an enormously successful model for the UK Company. It was in production for ten years and was ranked 'Machine of the Year' for five consecutive years between 1968-1972 -- a pretty mean achievement by any standards.
The bike's frame and use of rubber bushes saw the Commando win a design award, while its smoothness and rideability made it a favourite, especially with the riding public of Great Britain and in the USA, where it offered a genuine alternative to high revving Japanese engines.
It was Norton's last twin piston engined motorcycle and undoubtedly has both collector and enthusiast appeal.
