.006 per inch of bore is the standard for all 2 strokes. Example- if you have a 2.500 bore your ring gap should be .015. This applys to stock cast pistons. If you use forged pistons the end gap will be a little different. These days manufactures send their piston kits with the rings gapped and ready to go. The only time i modifiy replacment piston ring end gaps is when i build a custom race engine. Piston to cylinder wall clearence should be .004-.006. All of this info should come with your new pistons.