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:
1: Cable routing and maintenance
The clutch cable should be routed from the lever around to the RH (Timing) side of the frame, under the fuel tank along the side of the upper back bone. The cable must not go under any part of the head steady assembly! From there it is routed OVER the diagonal side bracing tube and down in front of the oil tank to the gearbox cover (Not under the tube, and definitely not through the wiring harness routing hole). Do not bind the cable down with multiple cable ties. Use caution when installing the fuel tank to avoid pinching the cable, and to ensure it runs underneath the tank from front to rear. The goal is to allow movement of the cable when the handlebars are turned, and to avoid tight bends and curves in the routing. This will help avoid a heavy pull at the lever and improve service life. The round barrel at the cable end which goes in the clutch lever should be free to turn inside its hole, and should be given a smear of grease for lubrication. If the barrel isn’t moving inside the lever, the cable is being bent with every pull and will soon fray and break. Cables are best lubricated with oil. There are tools available for this purpose, and proper lubrication extends cable life and ensures a smooth, easy pull. Aerosol type spray lubricants are better than nothing, but oil is best on clutch cables, providing superior staying power and lubrication. Avoid getting moisture inside the cable when cleaning your bike, as the cable will soon corrode inside causing added effort to pull and reducing it’s lifespan.
To adjust the clutch cable, first remove the access plug at the rear of the primary cover. Use caution in selecting a tool, as a loose fitting tool will usually gouge the slot in the cap. A stubborn cap can often be removed by heating the surrounding portion of the cover slightly with a heat gun or plumbers torch. (Use caution around ignitable materials (Fuel, rags, cleaners etc.) and gloves are a must!) If it’s still stuck a light rap on your tool with a small hammer can sometime ‘shock’ the cap loose. There are multiple variations and manufacturers of tools for these caps. I personally use an open ended wrench, which has a thickness at the open end perfect for fitting sideways in the slot. Inside you will see the clutch adjuster, which looks like a large slotted screw retained by a six sided nut, in the center of the clutch spring assembly. Loosen the clutch adjuster retaining nut with a socket (3/4 American) and back the adjuster out a couple of turns. Be careful not to drop the nut or adjuster inside the primary case. Next back the cable adjuster at the handlebar off completely. Now you can turn the adjuster in the center of the clutch in until you feel it touch the pushrod behind it. Once you feel it make contact, back the adjuster out a full turn and lock it down with the retaining nut. Once this is done, adjust the cable at the handlebar until there is about 1/16 inch free play at the lever before the cable is under tension. The goal here is to have no pressure in the clutch cable and pushrod set up when the lever is disengaged.
Continued in Part 2