I recently had my clutch/primary apart to fix a minor oil leak from the primary cover........the clutch had been working perfectly so no issue there........But upon reassembly, I tightened the C20 nut with my 1/2 inch rattle gun and i'm sure it tightened to the next slot on the nut........This after full assembly of the clutch, showed the symptom described where the outer plate was free and 'Clunking up and down" but the kickstart was difficult to push down freely......... This assembly actually had no shims under the C20 nut........ I removed the nut and took a light shave off the inner flange face in the lathe........maybe 10 thou at most, probably 5, then I polished the smooth surface of the nut, and smeared a very, very light amount of engine oil inside the C 17 bush........reaasembled, and now it is free and releasing fine........The C 20 nut needs to be tight or else the C3 will start moving on the mainshaft spline and this will cause further problems down the track.......be careful lubing the parts, as with heat and centrifugal force it will throw out into the drum causing possible slipage. I use a tiny amount of antisieze on the C5/1 shoe pivot pins, as these wear quite badly after much use.......Cheers and good luck to one and all.......