What oil you using?

Well, I don't Know of anyone else using that, I don't Know if it's got friction modifier in it,
But
I've seen the wrong oil cause that.

Oldfeller--FSO wrote on 05/26/10 at 16:05:05:

Friction plates are absolutely clean and no glazing ?
If so, try heavier springs if you haven’t already.

1) You said you sanded the steel plates ,but did you clean the fiber plates in gasoline ,soap and water and lightly sand and allow them to dry and oil them before installing?  2) you didn't have room for both an added steel and fiber ( your fiber plates would have to be worn almost to the service limit to allow this) ,so it makes sense to add only a steel . 3) semi synthetic oil is no better than regular oil ,it's a rip off , use regular oil or a full synthetic, and check to make sure the oil use doesn't contain Moly, 4) don't shim the clutch springs, just make sure the springs are of equal free height and in the service limit. 5) the rod should be between 12 and 12.5 mm  6) be sure to lift the arm near horizontal when reinstalling the side case ,so that the end of the rod engages the throwout ,rather than slipping between it and the case and jamming, not allowing to move.

Not Moly 4 ,just Moly . If you haven't got access to Rotella T4 or T6, Moble V twin would be good.

If your clutch is slipping, you might wanna listen to the people who ride these..

Ditch the oil with moly.