Found the thread you were talking about, great information.

I tried some 800 grit, but I'll give the 400 a try also. It's worth noting that the engine ran o.k. as a trimmer, but seemed a little soft. I'm hoping the new piston/ring ass'y will give her new life. Oh, and the mods you and Combat are laying out for us might help too, and maybe the CDI also,.....I'm looking forward to getting it going. Just need to figure out how to mount this thing in an airplane.