Can anyone tell me if a vintage Saito FA40 (exposed rockers) is supposed to have a piston ring. I decided to de-gum mine and was surprised to see that the ring was not there. Can they break up a vanish?? There is a shallow groove around the top of the piston that I would have thought was there to take the ring. Maybe the very early ones had no ring, just a groove. Doubtful me thinks !! I do know that the current models have a ring. Any help appreciated.