The introduction of the Norton Commando included an entirely new clutch design from the earlier Norton twins. Designed by Laycock Engineering, the new design featured a diaphragm style spring, along with a triplex chain replacing the original single row primary chain used since the twenties.
This was a much needed improvement, allowing the old Norton twin design to carry on through the mid-seventies while coping with the increased torque of the Commando motor. The design is fairly unique for a British bike, but it is an excellent design when set up and maintained properly.
The original set up used four fiber type friction plates along with three steel plates. A steel pressure plate was installed on the end of the stack. The diaphragm spring presses on the pressure plate when loading the clutch assembly. The entire clutch stack was held in clutch basket with a large circlip.
Starting at SN 212278, the clutch was updated to use 5 sintered bronze plates along with an additional steel plate. The steel pressure plate was thinned to provide space for the extra plates, and the clutch center was hardened by heat treating to improve service life. Before attempting to dismantle the clutch, it is important to obtain Norton service tool # 06-0999. This is the clutch spring compressor, and should be included in any Commando owners tool box. Without using this tool, the diaphragm spring will be violently ejected when the retaining clip is removed, possibly causing injury. Use caution! A properly set up Commando clutch should neither slip nor drag under load. It should allow for easy selection of neutral while idling, and not require Popeye style forearms to pull in the clutch lever. There are a few areas to address in achieving this happy state:
The AMC gearbox is one of the most successful of it's type ever designed. It has found a home in everything from AJS singles to fast, racing Commandos. It has a simplicity and robustness that makes it a favorite in Tritons and other specials.
After Associated Motor Cycles took over Norton in 1953, the gearbox was taken on as a project to be set up for use in multiple applications. The four speed AMC box was used first in AJS and Matchless heavyweights in 1956. In late '56 the box made it's way in to the 1957 Dominator 88 and 99, ES2, International and Model 50. The box has a history that extends back to the earlier Burman four speed gearbox, and from there to the even earlier Sturmey Archer box. They are so similar that some parts are interchangeable across the board.
If you’re in to British bikes, you know the name Amal. Often cursed with the vitriol reserved for Lucas components, the Amal carburetor is much maligned and misunderstood. It’s job is deceptively simple, deliver fuel to the motor. In practice this is much more difficult than it sounds. When you factor in that it was built down to a price, using questionable materials in such a way to be practical for myriad makes, models and purposes, the success of these instruments becomes more and more impressive.
The Amal Concentric carb was a development of the earlier Monobloc. It’s the most common Amal carb, used from 1967 on up. (It was later developed in to the Amal MK2 Concentric, but here were going to focus on the original Concentric.) The name was meant to showcase the fact that the main jet was in the center of the float bowl, as opposed to the somewhat compromised location in the previous Monobloc model with a side mounted circular float chamber. It was ubiquitous on British bikes through the late sixties and seventies. They fell out of favor, along with British motorcycles in general, as they were overshadowed by more modern and practical offerings from Japan. The design of the Concentric was well suited to the old style Brit singles and twins, but they did not work well with the multi-cylinder models being developed at the time. The main issues being the lack of any suitable arrangement for linking them together to a single throttle cable, and the overall height of the assembly. The attempt to rectify this issue on the three cylinder models from Triumph and BSA only highlighted these problems, making the carbs even taller and the throttle pull heavier. The Amal Concentric is still available today from the Amal Carburetter Co. and has received improvements in materials and production along the way.