One of the skis I put new rings pistons and bore. I got it all togeth and let some one ride it. Well the water line came off and got hot. really hot. I lost compression and it ran like poo. Well I took it all down and had it looked at. The head is flat and fine. the bore is still good. He ran a hone down it realy fast and there was no dark spots. So it has to be the rings. Pistons look good as well!
The other one is on my ski that I have had electrical probs with. It runs great then like crap then no spark. Well I tryed to get it to run and the dam thing back fired bad. It blew the water box in half. I also lost compression. I put some oil in the head and checked it. It went back up. I took the head off and the gasket looked good. The piston in the front of the ski can move more than the back as well. That is were I lost the most compression. So I think it needs new rings.
Oh and I can only get STD or 1M over at yamaha. I need STD and .5M over. Thanks. PM me some prices if you can.