RE: 63 FZ top end rpm
My engine had no compression and now with the new ring, it has a massive amount of compression. Its actually truely amazing as over time you forget. I think the rings on these little motors can wear much quicker as they are turning a lot of revs and the ring is serving double duty up stroke and down stroke.
I think the ring and the bearings will almost be a given on just about any used YS motor unless you are very lucky....everytime I buy a used motor the bearings are like a 90% guaranteed replacement. Most folks have let the motors sit in their garages for a minimum of 2.5 years before they finally motivated themselves to sell it.
I'd hate to see you get another used motor and find yourself needing to do the exact same thing minus one minor $10 part here or there.