Sounds ominous John [if that's the word]. What happened?.
l rebuilt the engine when l first acquired the bike, l noticed a part of the crankcase had been broken away, there is a flange of casing that holds the right side bearing on the mainshaft from sliding away from the clutch. l figured that the step on the shaft would stop the bearing moving on the shaft, and the left end of the mainshaft would just push against the left casing, stopping movement in that direction.
With the bike idling and a little pressure on the clutch lever, you can feel the lever pulsing. l gather that with a helical primary-drive and slight mainshaft end-float, l am feeling the movement through the clutch lever.
l imagine it is only the .5mm that l set the shaft end-float to, but my concern is what effect it may have on the shift fork on that shaft.
l am still going to test it this Sunday, the bikes first outing, l'm sure a few issues will arise :-)