Norton Commando History
Powered by a 750cc parallel-twin later enlarged to 828cc, the Norton Commando was offered in several models to fit the needs of different riders. Performance, mechanical simplicity, and a unique engine mounting system are all hallmarks of this classic British machine.
Throughout the forties and fifties, British bikes dominated motorcycle performance and racing venues. However, by the late sixties, Japanese manufacturers started producing faster, cheaper, and more reliable motorcycles, severely cutting into the sales of both British and American-made bikes.
The Norton parallel-twin engine was powerful enough, but suffered from vibration at higher speeds. Previous attempts at rubber-mounting the engine helped marginally. The company had neither the time nor money to develop a new engine.
Norton's Chief Engineer Bernard Hooper, Dr. Stefan Bauer, and assistant Bob Trigg, devised a system where the engine, gearbox and swing-arm assembly were bolted together and isolated from the frame by special rubber mountings. Instead of the engine being rigidly bolted to the frame, it is hung off the main frame, via two cross-frame tubes, one at the front of the engine and one at the rear of the sub-frame. The suspension system kept the swing-arm true in relation to the engine position, while isolating the rest of the chassis from the vibrations of the engine.
Norton took their 750cc Atlas engine (actually 745cc) and developed a new frame, tipping the engine slightly forward. Bolts holding the powertrain assembly to the main frame passed through rubber buffers in the tubes, isolating the engine from the frame. This allows the engine to "float" on the vertical plane, with lateral movement controlled by shims in the mounts. This eliminated the extreme vibration problems, effectively separating the rider from the engine.
The Isolastics anti-vibration system did reduce vibration, as long as the required free play in the engine mountings was at the correct level. Too little play brought the vibration back and could crack the frame, and too much play brought handling issues, particularly fishtailing in high-speed turns.
750 Norton Commando
Soon after the 750cc Commando Mark-1 Fastback was introduced in 1968, it was joined by the 750-S model, having high-mounted left-side exhaust and a smaller 2.5 gallon gas tank. In 1970 the updated S model, called the Roadster, had conventional low exhaust pipes, featuring upward-angled silencers with reverse cones.
September of 1970 saw the introduction of the Fastback Mark-2, with a modified stand, chain guard and alloy hand levers. The Street Scrambler and the Hi-Rider appeared in 1971, along with the Fastback Long Range, which featured a larger gas tank. The twin leading-shoe brake drum up front was replaced by a hydraulic disc brake.
Norton Commando Hi-Rider
Nearly parodying bicycles such as the Schwinn Sting-Ray and Raleigh Chopper, themselves parodies of Harley choppers, Norton rolled out the Hi-Rider in 1971. A variant of the 750 Commando, the Hi-Rider featured a high handlebars and a "banana" seat with backrest and short sissy-bar at the rear.
Other features on the Hi-Rider included a small headlight and small 9-litre (about 2.4 gallons) gas tank. Although it stayed in the line for several years, few Hi-Riders were sold. Curiously, it outlasted the high-pipe S-model.
Norton Combat Engine
In 1972, the Combat engine was introduced with the appearance of the Mark-4 Fastback, along with an updated Roadster and the 750 Interstate. The Combat delivered 65-horsepower at 6,500 rpm with a 10:1 compression ratio, but main bearing failures and broken pistons were often encountered.
750 Commando Mark V
The last of the 750 series, the Mark-V was produced from November 1972 to mid-1973 as a 1973 model. Engine bearings were improved, and compression reduced to 9.4:1, both helping engine reliability. 1973 also saw the Long Range model discontinued.
850 Commando Mark 11
Starting in January of 1973, the Mark 5 Fastback was launched and the Long Range was discontinued. Commando engines saw an increase of bore and stroke, now 77mm x 89mm, displacing 828cc and advertised as 850cc. The Roadster, Hi Rider and the Interstate all began to use the larger engine.
The earlier 750cc cylinder head, well designed and factory-ported, was retained. Compression was further reduced to 8.5:1 with the engine now producing 60-horsepower at 5,900 rpm. Increased torque from te longer stroke seemed to make up for the reduced horsepower. In 1974, the Commando lineup included the Roadster, Mark 2 Hi Rider, and Mark 2a Interstate.
John Player Norton Commando
Introduced in late 1973 and reaching the public in 1974, the John Player Norton (JPN) Commando was essentially an appearance package and was mechanically stock in every way. It was available with either the 750cc short-stroke engine, or the Mark 2A 828cc engine. Approximately 200 John Player Norton replicas were produced and all had right-side shifters. Although common now, it was an original marketing concept to homogenate a race bike into a street bike.
850 Commando Mark 111
Due to popular request, electric start was introduced on the 850 Mark III Commando. Fortunately the kick-start was retained, as the electric starter was not totally reliable. A front disc brake also appeared around this time.
read Kick-Starting An Old Motorcycle
For the Mark III, the Isolastics system was upgraded. A paired-spring rated to carry the weight of the engine and transmission assembly was designed, taking the load off the Isolastics mounts.
Right-Side to Left-Side Shift
In 1975, new federal regulations required all motorcycles sold in America to have left-side shift and right-side brake controls. The Commando's competetors bikes also switched from right to left, including the Triumph Bonneville and the Harley-Davidson Sportster.
The Commando models, now weighing 460 pounds, were now reduced to two, the Mark III Interstate and the Roadster. A rear disc brake replaced the previous rear drum. These two models remained unchanged for 1976.
Last Year Norton Commando
The last year of Norton production was 1977, with the Commando Roadster and Commando Interstate. It is estimated about 1,200 bikes were built in 1976 and 1977. Just 30 units were sold in 1978, which were actually leftovers from 1977.
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From 1968 until the demise of the company in 1977, the Commando was the main bike in Norton's lineup. It was the last of the Norton parallel-twin machines.
Norton Commando Performance
In the March 1970 issue of Cycle magazine, tests were made on all then-current superbikes. Of the seven bikes tested, a Norton Commando-SS ran the quarter-mile fastest, at 12.69 seconds. The Honda CB750 stopped more quickly, but the Norton was faster.
Norton Commando Problems
Although the Norton parallel-twin engine was reliable and well-engineered, the bike's electrics were suspect and accounted for a fair amount of breakdowns. However, over the last several decades, many component updates and improvements have been offered. Commando owners in general don't seem to be quite so obsessed with originality as are some other marque's. Examples with sensible modifications often bring as much as 100% original machines.
The Isolastics anti-vibration system, while reducing vibration, needed regular maintenance. On the last Mark 111 Commandos, adjustment was easier, and a conversion to the later Isolastics is available for earlier models.
Another area of concern when restoring a seventies Norton are the nuts and bolts. On a 1975 Commando Mark 111, you will find a combination of metric, SAE, and Whitworth sizings.
The Norton Commando is one of the most prized bikes in today's classic motorcycle market, having excellent performance and good parts availability. Over the years it has remained one of the most desirable classic British bikes, and many will argue it was the best.