I had a similar problem before I started switching from the aluminum clutch plates to the steel plates. When I took the clutch pack out for inspection and installation of steel plates, I found that the aluminum plates had worn so much that they had a dish on each side worn in by the fiber plates. I swapped to steel plates, and viola, all was right again. While I never really figured our why in the world worn aluminum plates would have such an impact, I surmised the following potentials:
1. As the aluminum plates wear, the clutch pack actually become smaller (when measured across the top of all plates), requiring more travel of the clutch arm/cable/etc. to disengage the pack.
2. The second potential was that with the available clutch throw, the fiber plates were still contacting the outside edge of the dish area worn by the fiber plates. With contact on the outside edges of the aluminum plates by each fiber plate, there was just enough drag to keep the clutch pack engaged to some degree.
Checking to see if this is your problem is quite simple.
1. Drain the coolant from the bike into a bucket.
2. Lay the bike on its side so the clutch cover is up.
3. Remove the kick start lever, and remove the bolt that engages the rear brake lever to the master cylinder (this will allow you to leave the peddle in place, but provide enough room to clear the clutch cover).
4. Remove the bolts around the clutch cover.
5. Gently pull the clutch cover free. Use a rubber mallet to help free the gasket seal, but don't use ANY screwdrivers, as this will damage the sealing surface. Also, if you are careful, you can even reuse the gasket. If if tears, dab a little case seal on the the tear during reassemble. Of course, the easiest thing to do is just spring for another gasket.
6. Once the cover is loose, wiggle it to help it pass over the kick starter shaft. You can also spray a little WD40 on the shaft prior to removal of the cover to help the shaft go through the seal.
7. With the cover off, loosen the 10mm bolts on the cluch basket. Remove the clutch pack and inspect the aluminum plates. If they are dished, replace them with steel.
8. Reassemble in reverse order.
I have assumed that you have checked the clutch play at the clutch lever. If you have run out of adjustment at the lever, you can always adjust the cable itself with a couple of 10mm wrenches. Essentially, if you have the proper play at the lever (about 1/4 inch is plenty), there isn't much you can do about how much throw you have at the clutch arm.
Good luck, and let us know what you find.
Rick
