Lapping,defined
Lapping,is the process of fitting one piece to another by using an abrasive compound.An example would be lapping the valves on a 4 cycle engine.The sp 125,has no keyway in the shaft,but relies on the taper of the shaft to hold the clutch in place.This taper acts similar to a wedge,with regards to its ablity to hold.An example would be the Morse taper used on large drill bits.Lapping has been used for years on the flywheel side,to get a more perfect fit and help eliminate out of alignment wobble.I suppose in a worst case scenario that a new keyway could be milled opposite the old one,but that would entail a lot of work and perhaps a sum of money.As far as a crank shaft inter change,it may be possible to interchange a super 44a with another 5.3 cu inch engine crank.It's 5:45 am,now but I wll look up some part numbers after I get off work,and make a post if I find any thing that might work.As I've said before,a lot of the "10" series will inter change and I wouldn't be surprised if a lot of the "1" series would also[the 44 series fits in the time frame]