Valve clearance problems???

oKiee, i have a 85 ATC200X with a 82 ATC200 motor with a newer ATC200S head i jist put on. Now the ATC200S piston has a indent in it so the valves clear(exhaust & intake) and i had to put that head on the ATC200 bottom end and that piston only has a intake clearance indent, and not thinkin i put it all together and it ran good but it would only go fer a few seconds the quit but you could start it up again it'd do the same thing, and i think that the ATC200 piston not havein the indent fer the valve to clear caused my cam chain to snap, cuz it ws very hard to turn over by the pull start, no electric, abd with the pull start off you couldn't've turned it over by hand.:muscle: So could i grind a indent so it would clear or do i have to swith pistons???Thanks