hmm, just pulled it all apart and the bore is buggered. but here is where it gets a lil interesting. the piston hasnt burst on its own accord....the valve has dislodged and smashed into it. AND it has the original valves. so what? well i took it to mnw who charged me 2 grand for a fair bit of work, and part of that was for new valves and a reconditioned head.