Re-seat the valves, a bit on honing on the head, and some araldite on the piston I reckon
Last time I saw a piston like that it was on a 50cc trials bike that the 2 stroke oil mix line blocked on.... the head split in two with that (and I fell off)!
How quickly would that have happened? Was it a slow failure and then rapidly ****ed up or was it perfect piston then BANG? Would he have heard (with hindsight?) something not right but did ignored it and 5 minutes later = bang?
"The piston looks like it jammed in bore, whether due to the top melting or being too tight, but the scoring on the bore and piston is horrible, then the wrist pin broke out the bottom of the piston, then on the next rev punched the piston up into the valves where it got stuck"
Apparently the engine was rebuilt just before xmas as it had been run dry of oil, spun a bearing and knackered the crank. So could possibly be down to human error rather than general wear and tear.
Looks like the oil feed to that piston was inoperative, Crispin I would have thought it would have shown signs of blue smoke & excessive oil usage before fatal failure.
Apparently the engine was rebuilt just before xmas as it had been run dry of oil, spun a bearing and knackered the crank. So could possibly be down to human error rather than general wear and tear.
Kind of suggests general neglect which could be the cause of the next problem (the catastrophic failure) or at least a contributor - oil is required usually except in the case of a company car ...
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