Custom builds and original restorations for all British motorcycle enthusiasts
IS YOUR CLUTCH A PAIN
Setting up a 3 or 4 spring clutch from an old Trumpie or Beezer.
I am assuming you have a taper hub puller and a slotted screw driver or T handle tool for the pressure nuts in your kit. So with the clutch plates laid out grab the cush drive hub if your model has one, pull and twist looking for poor cush rubbers or loose screws. Either or both probable if unattended for a long time. Turn the cush unit or other type inner hub and look for chain wheel wobble. If minimum to none, which would border on a miracle and rubbers appear good, another miracle, proceed to assembly. If a problem this is where a puller is a good thing. I use a rattle gun to coax the hub from the mainshaft taper. When broken down to taper hub, rollers, thrust washer if your model has one and cush assembly, take one side off the cush hub to inspect rubber or replace them. Best to tighten all 6 x 2ba screws with an impact when done, as is the case with pre 750 Triumph and A65, some tread locker wont hurt. The 750 models have 3 x ¼” bolts and are a more sturdy unit, progress. They will work in earlier models. I have seen untold butchery on these 6 screw types over the years. Amazing what people do. These screws are cheap. Not uncommon to see these screws loose and the whole cush drive unit falling apart. I also made a tool using an old taper hub and welded a bar to it so one can lever against the rubbers to fit new ones, they are hard to fit otherwise. Resist cutting them for an easy fit. With that done, or before, check taper hub on shaft with woodruff key and without key to compare fit on shaft, look for rock or less than firm fit. Sometimes the key can be a bit wrong and some material can be filed from top of key to ensure a good hub fit to the taper . If the mainshaft taper is compromised , ie, has seen a slip and has key material welded by friction to the shaft and inner taper hub surfaces or the mainshaft is actually bent then the Do Do just got a bit deeper. It may have just been hanging in there. Sometimes the shaft can be cleaned up enough to get a reasonable fit to a replacement taper hub, or the original if build up minimal. Take some linishing tape and with bike in top gear spin back wheel whilst holding on hub to the shaft. You will soon see if this is going to work. If minimal or when taper is a bit cleaner try some grinding paste, again holding hub to shaft and spinning wheel. Hold lightly. Another way is to remove kicker cover then with a socket and drill have a friend turn shaft slowly whilst you hold hub to shaft, lightly.
Anyway, assuming the shaft is straight, (if not then with a bit of luck and a steady hand one can fit a new one without complete gear box strip on a Triumph, slide out slide in), the taper is in as new condition, the woodruff is a good fit and the cush drive is in very good condition then before assembly you need to dress the steel plates. This is done at my gunya by me using 2 magnets and a 6” floor mount belt linish machine. You could use a sheet of 400 grit or grittier on a flat surface. Working until you achieve at least 80% flat surface on both sides. Even new ones aren’t flat as they are a pressing. This is the most critical part other than a straight shaft, a good taper and good cush hub. I think I already mentioned them. With the plates all flat, and the bonded plates all cleaned or replaced, assemble. Maybe a new thrust washer will be required on unit era machines, two types there. The rollers rarely need replacing. On a pre-unit Triumph I often take the shoulder off the cush hub and let an extra bonded plate into the chain wheel. The standard design places all the clutch pack pressure on the steel plate resting against the lip and not the chain wheel as the later models do. Be careful to make sure pressure nut screwed pins are free when fitting cush to taper. On early A65 BSA models which had a beautiful chain wheel setup for a couple of years with the rollers in a plated and screwed housing but more expensive to do I’d think, designers were forced back to the cheapie version by number crunchers, I’m sure. With all A65 models one has to look for long taper hubs. I have found them regularly and it can cause a rattle. This is the taper hub spline where it fits into the cush hub spline and sits proud. To keep things tight the taper hub needs to be below the cush spline shoulder where the thick hold down washer sits. If not then the cush is left loose to work away and cause a rattle . Have seen and heard this often. On my A10 and B- single stuff when possible I opt for a Triumph chainwheel and taper conversion hub as factory fitted to late era A10. Ok, so run a file over and along all the grooved edges on the cush hub and chain wheel as well as the bonded plate tangs, just take the rough stuff away. When done and assembly on the shaft I always tighten mainshaft nut with a ½“ rattle gun, with nut home, a couple of extra tap-taps makes a secure assembly, done hundreds over 50 yrs, but best not tighten nut on other end of mainshaft the same way unless shaft can spin, done hundreds and snapped the thread of one shaft when shaft couldn’t spin with clutch pack still attached, learning curve took a steep incline. With it all together leave screws 2-3 threads below pressure nuts slots, never expose threads on the screwed pins. That’s what the less than enlightened do when trying to stop clutch slip. There is no need for big spring tension when all has been corrected, in particular the steel plate flatness which is key to a light 2 finger, non slipping clutch. Finish up by adjusting out the wobble when slowly kicking through with clutch lever pulled in. Getting this as close as possible to true, goes a long way to a better ride with nice even clutch take up. Equal length or new springs will help make this easier. Always relax the cable adjuster first before adjusting the push rod on any bike. Late models have a mechanism that can be checked for lift, but most rely on a deft hand. Again, always make sure cable is slack before attempting any clutch pushrod adjustment, turn adjuster until it touches, then back off ½ - ¾ turn. This gap will close a little after some use, especially if you opted for new bonded plates. If you ever get clutch slip, relax the cable and check the rod clearance first. Leave up to ¼” slack at the lever but leave some. To oil the cable which helps, I take it from the lever, tie in an upward position then make a small paper funnel, tape to cable end and fill with oil, leave to drain in. Helps a lot. Cheers, Brian