How far should the friction disc be seated inside the drive pulley hub?
 

On my 129, I had to get new set screws for the disc. It seems that if I push the disc in so that the complete thickness of the disc is inside the hub, the set screws will wind up tightening against the eccentric collar rather than the bearing. Shouldn't it tighten against the bearing? A quick search came across this older thread. I'm going to go with the pictures that show the teeth inside the hub but not all the way in as suggested in the manual. I see there are some sort of springs that are part of the whole pto clutch assy. If there were originally springs on there, they've been gone for decades!!

I'm sorry, but photo's are really going to be helpful here,
I'm having a difficult time trying to picture what you're saying.

I'm a bit confused with your post/question.... however, here's a link where you can learn more about your PTO: https://www.onlycubcadets.net/forum/showthread.php?t=9

The hub will only go on till the snap ring inside the hub stops it against the bearing so it can't go on too far unless the internal snap ring is missing ?? I think on that model the bearing is locked flush with the end of the crank ?