My mates TT 225 has died. So been helping him investigate the cause. Compression test showed cylinder 3 with a low compression. So we pulled the head off in hope that it was an issue with the valves. But not such luck. Found cylinder 2 & 3 to have some damage to the pistons. All the pistons have evidence of contact with the valves but I think this happen before he bought the TT, as he has an invoice for some work done to the head and there is no damage to the valves now. The pcv system is also poked, as there is a lot of oil in the intake system and throttle body is pretty dirty. There were some random bits of metal inside the cylinder that has been beaten around with the 3rd cylinder taking the most damage. Anyone have any ideas of what's happened?