Bar Keepers Friend, nice recommendation. I hadn't thought to use it. I use 3M Perfect-it ll, a final polishing coumpound for show car finishes. When lapping with light pressure It doesn't remove metal, just carbon and dried fuel components.

Saito's rings are interesting. Unlike OS, they leave radial grinding marks on the outside of the rings for faster break in......I guess? After a gallon or so of fuel burned the compression is usually rock hard, taking over 30 sec to bleed off cylinder pressure when held against the compression stroke. Of course Saito cylinders are also very close to perfectly round from the factory, which doesn't hurt either. At any rate it's easy to tell how much run time Saito rings have on them by examining the remaining grinding marks, if any.

I have been using Bowman rings as replacements on 4 strokes for a while now. They break in even faster than Saito or OS rings. Byorn at Bowman/RMJ claims that his rings are fabricated from a softer cast iron and use less tension than other factory 4 stroke rings. I like them a lot.