Motorcycle Repair: RZ500 clutch skipping, the return! :-), wheel lifts, linkage problem

Question
Hi Mike,

Yes, I exhausted the possibilities of regular clutch slipping, I have another RZ500 which clutch slips when transmission oil is cold, I also have a slipping cluth on my RZ350, and it is really not the same behavior, it is really like I would use power clutch technique. Sometimes, the front wheel lifts when I really open the throttle in first gear...
For the rest of the gears (2 and up) there is no sign of slipping nor skipping, and trust me I tried hard! ;-)
The clutch I put back in when I rebuilt the RZ500 is an used clutch, but all plates are within Yamaha specs...
When I encountered the problem the first time, I changed the fiber plates for Barnett's Plates (They are used too) but the behavior is still the same...
I think that the clutch is faulty because if it was a transmission gear or fork problem, it would disengage and would not re-engage and I would probably hear a gear grinding sound...
I suspect that some steel plates may have overheated and like disc brakes have harder spots and skips on these spots...
I checked the steel plates for warpage but they seemed ok.

Thanks again for your time!

Answer
Gino,
 Yeah, it's possible the plates are glazed and just not giving you the best adhesion they once could.  More or less, I agree w/ the unlikely linkage problem.  Gears are either engauged or not, there's no in between.  Let me know if a new clutch kit does it, steel rings and fiction rings.  Yeah, be sure that pressure plate has no runnout.  There may also be stiffer aftermarket springs availible although you should only really derive benifit from them in extreme situations.  

Good luck,
Mike