Does your clutch tend to drag even with the proper hand lever free-play and clutch lifter adjustment? I just found the cause of my frustrations.
The pivot hole in the hand-lever was worn, as well as the pivot bolt. The hole was elongated by .030", and the bolt was .014" smaller on the worn side. Even with the cable over-tightened (which would have caused the clutch to slip), there was free-play at the hand lever. I had a spare lever and bolt that were in much better shape, so all is well now. I guess when you grow old with your bike, this type of thing can sneak up on you!
I took a couple of pics; in the second pic, the crescent above the bolt is daylight.