cooked rings - Snowmobile Forum: Your #1 Snowmobile Forum

rosem1231 · 03-12-2008, 07:00 PM

My buddy just bought a 99 mxz 670HO with 1500miles. Did 80 miles then had complete engine failure. Pulled the head and it seems as if he blew the rings. They are now melted into the top of the piston, and scored the head. It had 125 psi before we headed out, and now obviously nothing. Plugs seemed OK, and it was using oil. Cylinder wall is barely scored, but I think it might be too much to hone. So, what causes the rings to fail like this? What can be done to fix this baby up?

zipper670 · 03-12-2008, 07:35 PM

Ya my brother in law has the same sled and it blew the rings on the mag Side cylinder two weeks ago. I think it was because he was ripping on the ice going 100 mph. the rpm’s must have been going threw the roof !! His sled was running mint all day until then. He just put a new piston in it and it runs like new again.

**smallengineguy** · 03-12-2008, 07:38 PM

Did helet the sled warm up before he rode it? Go to the engine section of this forum and click on the piston diagnosis thread and see if you can match any picture.

rosem1231 · 03-12-2008, 08:41 PM

SEG, cool link. If I had to choose one, it most likely resembles the smashed debri piston, in my case though, there is much more debri. There is actually silver chards of metal built up like a pancake on the top of the piston. It pushed up into the head. Any ideas? Ever hear of anything like this?

**smallengineguy** · 03-13-2008, 07:20 AM

You might have lost a rod bearing on it. Remove the cylinder jug and piston, then see if the rod bearing is OK.