TomB,
Is the dry sump equipment secondhand ? Sounds like you may have a bent clutch arm, these used to fail regularly . CC uprated the the clutch arm 1999 ish the uprated ones do not fail.
Just look at the action of the arm within the cut out in the top of the belltank, if its hitting or its movement is restricted by the belltank casting then suspect the clutch arm.
Rob