damage descriptions

[pcsummit]

I will be ordering a new cylinder kit, but I am more interested in the cause rather than the effect. One cylinder looks normal and had 130psi compression using screw in guage. The bad cylinder had 0-30psi and the piston has a 1 1/4 inch chip missing right at the exhaust port side of the top. The rest of the piston top has nice sharp edges and does not appear to have excessive wear. note:155hrs on ski.

The ski runs on the one cylinder, lots of unburned oil/gas comes out the exhaust so I really don't suspect lean operation. Any advice would be appreciated.

Mark
Yamaha 800xlt 2003

[Technical Support]

Re: damage descriptions

We need good pics to diagnose it further, please.