The Norton Commando History

Although shown at the Earls Court Show 1967, the Norton Commando was to buy just in April 1968. The experiments with the P10 800cc twin-cylinder with overhead camshaft were not very promising, so the Atlas engine whose base left over from the 40s, still had to hold out a few years; Regardless of whether the responsibles liked it or not. The old specter of vibration was avoided by the development of a new frame in which engine and rear wheel formed a unity. The driver and the rest of the machine where separated of the disturbing vibrations by the rubber mounting of the engine-rearwheel unit . Between 1967 to 1976 at least 10 different models where built, which mainly differed in other tanks, seats, exhausts, handlebars, brakes and other color schemes from each other. These differences are mentioned here only in passing. In this review, only the most important changes are mentioned. The transmission remained the same AMC device that received only one significant change: A longer main shaft to accommodate the new Laycock diaphragm clutch and the triplex chain. Everything was packed together into a new, oil-proof housing made of light metal. This principle was years ahead from the thin housings held a single chain . The alternator was still at the end of the crankshaft. The ignition with 2MC capacitor was first still behind the engine. The crankshaft had the same stroke as the Atlas. The metal content of the crankshaft has been modified to take account of the new rubber mountings for the engine. The compression ratio of first 8.7: 1, then 8.9: 1 gave together with the machining of the cylinder head a power of 56 PS at 6500 rev / min. The carburation was still covered by 2 30mm Amal Concentrics. The new machine was designed by Bernard Hooper and Bob Trigg under the direction of Dr. Stefan Bauer.


In the first year of production, the engine was still almost the same as the Atlas engine. It was tilted just slightly forward. This sounds quite simple. It was more complex then, to bring the production up and running in a way the produced Number of Bikes was satisfying the outstanding orders.


This year, for the first time the "S" appeared. This Model had a small gas tank and the two exhaust pipes were on the left side on about half of the bike height, way out backwards. But the design proved to be too radical for the United Kingdom of those days. Despite its power, this model did not sell particularly well, and therefore in 1970 was taken from the program. The extra power of the "S" was achieved by somewhat lower back pressure of the raised exhaust system. The only significant change I would mention is the shift of the ignition to the front of the engine. This change was made at the same time as raising the compression ratio to 8.9:1 implemented together with the limitation of the speed at 6800 rev / min. For the first time were Peashooter (countercone) silencers where used. The Fastback still had the old Atlas silencer untill the end of 1970. At this time, the fastback was designated Mk.ll. With the introduction of this term the Peashooter silencers have been introduced for the Fastback.


All Models from 1970 had the new ignition and the new tachometer drive; The Peashooter silencers have been introduced for all models. A production racer model came out, which quickly received the nick name "The Yellow Peril" because of its coloring. A changed compression ratio of 10.25:1 and other tuning procedures screwed the performance of the production racer up to 70 hp at 6500 rev / min. The production racer came with a disc brake. In the same year, the Roadster was introduced, which looked a bit like a body double of the S-Type with a more conventional exhaust layout. All models received a new rear hub with damper cushions instead of bolts and cap nuts, that have been used since the 1940s.


Was there some model and cosmetic changes. But nothing notable was changed at the engine until 1972. By searching for more performance and the associated changes to the engine, lack of foresight, inadequate long-term tests and the sloppy production and quality control retaliated.


The mentioned looking for performance culminated in the so-called Combat engine (from engine no. 200976). This had black cylinders, and an output of 65 hp at 6500 rev / min. This was the highest performance ever offered for the engine in series production. The displacement was still increased, but without surpassing the power of the Combat engine. This performance increase was mainly achieved due to the abrasion of 1mm Material on the cylinder head, which in turn a modified compression ratio of 10: 1. But there where forgotten an important point: The abrading of the pushrods. Because the angle of the rocker arm was no longer correct, and the rocker arms got in contact with the cylinder heads. Another problem in this field were the spiral valve springs, which have been facilitated by the omission of the insulating washers under the inlet valve spring plate. The Achilles heel of the engine came now only too clearly in the foreground. The crankcase was overcharged, and damage within a few thousand kilometers were common. The crankcase has been reinforced subsequently, and the ball bearing on the control side replaced by a roller bearing. However, these improvements based more on speculation than on concrete investigations. Sosoon became apparent that the crankshaft was flexing so that the rollers of the main bearing scuffed and all dissolved again. The next step was then to investigate what was really going on. One of the main causes of this disaster was that the centrifugal force was that the ignition advance assembly was'nt up to do his task. The vibrations and bumps transmitted to the controller afflicted it in such a way that it got stuck in almost any position. In nearly every case it got stuck in the maximum advance position. The engine shook the crankshaft right through, but due to the isolation of vibrations against the driver, the driver did'nt notice this irregularity. But it got even worse: Due to a deep oil groove below the oil control ring, the piston crowns tore down. To get rid of all the mistakes, new so-called superblend crankshaft bearings were installed. They had barrel-shaped rollers which allowed the bending of the crankshaft without scuffing the bearing. To eliminate the above problems, a more stable centrifugal ignition advance assembly from Lucas and new Hepolite pistons were used. Simultaneously with these changes appeared in the accessories market appeared the first electronic ignitions from Boyer-Bransden or LUCAS. There was even a small change that characterized these new engines: The engine ventilation was moved from the left end of the camshaft to the oil sump. A welcome addition was a cartridge oil filter, which was mounted between the motor mounting plates behind the gearbox. Newly there was a so-called high lift camshaft, known as SS. Norton later develpoed "sharper" camshafts, namely the SSS and SSSS (Triple S, S Four, or 3S and 4S). These sharp camshafts were never incorporated into a series motorcycle (Exception: Production Racer). The Combat engine was the first engine which was equipped with 32mm carburetors. Although by now found on all engines, the intake diameter remained 30mm, which allegedly contributed to the improvement in torque. This significant power raise also showed the limits of conventional brakes, so that disc brakes were introduced on all models in 1972 for the first time. The Fastback was produced another year. The Roadster was available until 1977, at last as 850cc. Responses from the European market, which required a shift away from small tanks and high handlebars, culminated in the interstate. Short gear ratios, mainly for the American market were lengthened to avoid over-revving the already heavily loaded Combat engines. Although all these changes were in progress, the older camshaft and cylinder heads with a compression ratio of 8.9:1 were built in for a short time. 1973 Superblends and 32mm carburetors were standard, but the compression ratio was left at 8.9:1. The latter was achieved by the use of a thicker cylinder head gasket.


The Commando started now, after all these warranty claims from the ill-fated Combat engine (resoved from engine no. 211110), slowly to establish again. Oil leaks and vibrations were still not healed, but at least the engine did no longer a selfdestruction in a short time. The stocks of pushrods with fallen Stellite ends were over, but the offer of to soft camshafts held for some time. This error was usually noticed after about 10,000 kilometers, than the peak power began to subside. It seems that the EN32 material used, had lost some of its hardness by the special "Tuftriding" process (hardening with Cyansalt). It took a long time until the customer had forgotten all these mishaps. These and the main bearing Saga stuck like glue to the brand Norton. Now the largest version of this engine, the 850, which 's displacement really was 828ccm appeared. The bore was enlarged to 77mm, and it was a miracle that the ribs do not fell from the cylinder. The cylinders were given a different look because the lower flange and the retaining bolts with nuts by cap screws have been replaced with bolts so that the cylinder head had to be removed first now. Removing the cylinder and the head as a unit was no longer possible with the 850s engine. The compression was 8.5:1 lowered to increase reliability, and to raise the output to 60 bhp (In truth, there were probably no more than 55 hp). The change in piston size got along with a slightly change of the crankshaft weight. The big, nut-alike oil filter, which was rejected by the Combat engine returned. Also new was the balance pipe between the exhaust manifolds, which should improve the torque in the lower RPM ranges. The Black Cap muffler and the new, black, plastic air filter, (both changes were imposed by Norton stringent noise regulations on the high-volume US market), appeared. Neither of these "innovations" was particularly beneficial to the performance, and so the air filter and silencer of the older 750 models was simply installed by many owners. Since the bikes sold well with the new 850s engine, the older 750cc engine (engine no. 230935 was the last 750cc engine) was removed from the program. Also in 1973 a few minor changes were incorporated into production more Superblend main bearing and improved Stellite ends at the pushrods


The new John Player Norton appeared in the presentation of the works teams: a white race fairing with blue and red stripes, along with the standard 850cc engine. The trim included dual headlights, who needed more power, which in turn requires installation of the high performance alternator RM23 from Lucas, to supply the battery with enough charge current. The JPN was always a sheep in wolf's clothing, only the 750 short stroke version was a real competition engine. This had the 77mm bore of the 850 but with a 80.4mm stroke. This engine was sold as a short stroke Ready-to-Race engine to provide customers with real racing ambitions. The works racing team in 1973 had some success with Peter Williams and Mick Grant, which occupied the First and Second Place in the Formula 750 TT. This and the reached average speed of 172.2 km/h were probably the main reasons for the good sales of the JPN. 1974 was a year of consolidation: While the quality standards have been improved, the model range shrank to the 850 Roadster, interstate and the soon suspended JPN. A new logo appeared on the instruments: The blue-and-white line that formed the letters NVT (Norton Villiers Triumph) was also known as Wiggly Worm. The merge of Norton Villiers Triumph was another attempt to avert the looming end of the British motorcycle industry.


On the this year presented MK.III a very significant change was the implemented: The foot shift lever was moved from the right- to the left side. As if that were not enough, an electric starter was realized yet (thankfully, and in most cases significantly, the kick starter was retained). These changes were required due to import regulations on the high-selling American market. There were many small changes to the Mk.lll. The vernier adjustment of Isolastics, although developed since the early Comando, but as it seemed to be too expensive for mass production, it was established just with the MKIII model into production. A rear disc brake and heavy duty alternator RM23 were also included as standard. The oil supply to the engine now had a check valve which prevented the leakage of the oil tank into the crankcase. The timing chain tensioner got a rubber coating and an inspection hole in the cover. The primary drive cover is provided with screw around, which allowed a better oil tightness of the cover. The primary chain itself was equipped with a hydraulic tensioner, whereby the transmission could be fixed in a set position. The crankcase breather is again displaced in order to avoid soiling of the starter. All this was very welcome news for the customer, but it was too late to save Norton. Although sales were sustained 1976, subsided sharply then in 1977, to halt completely in 1978. This sealed the end of the Norton Commando.