Picked up a 99 Yamaha GP800. Front cylinder had 33 PSI rear had 108 PSI, so I knew it would be a project. I tore down the topend, and found that the front cylinder was indeed scored... Based upon the damage it appeared that the piston ring locator/retainer pin backed out and allowed the ring to spin around and catch on port. I was still concerned on why this happened though? I have a new wiseco stock bore kit on the way, except I need to find cylinders... any advice, and what it should cost? The rear cylinder also has some minor scoring, just enough to barely catch my fingernail, so Im going to just replace both.
The two main questions I have, are:
1.) do the valves look okay? it appears theres no chipped pieces but not for sure, should I clean them? if I should replace, where should I get them?
2.)I have an oiling issue it appears... maybe this is what caused the pin to back out? The rear cylinder has a puddle of green clean oil in the base of the case, and is coated with that oil, the front (which is the one that spun a ring) has no clean green oil at all, and the base of the case has a real small puddle, but it isnt green. However, when I pulled each small oil line off, the oil was right there, and the hoses were connected as they should be. If it was the oil pump that failed, wouldnt both sides run dry, not just one? I will probably delete the pump and premix it, but I'd still like to know what you guys think the issue is that caused this.
Thanks for reading and looking forward to responses.!
