Thanks for the input. I have two more Ryobis disassembled and getting converted. I will wait till prop balancer arrives before having the other flywheels turned.

At least I will have a static references even if I never use it.

One engine still had some casting alum OVER a large part of the magnets. It also had much more carbon in the exhaust port (over 60% closed off, a frozen ring and a lot of varnish (?) residue in the lower end. Cleaned up OK. (Used oven cleaner on the piston to help loosen the ring, which broke but made a great to fit scraper, once it was dressed on grinder, to clean the ring recess.)

Would the Alum over the magnet reduce the magnetic field enough to have given a reduced spark to the plug over its lifetime to date?

My thought is to have it turned down uniformly till just the magnet is lightly surfaced. The gap had to be wide for its life to date.

Any problem in just facing the magnets while in the lathe?

Mike