'04 Mountain Cat 900 question

[iride49]

Last spring I busted a piston ring and it scarred the cylinder wall and got sucked out the exhaust. Picked up a new cylinder and a wiseco piston and installed a month ago. Ran great. Went out today and the exact same thing happened to the other cylinder. Didn't even get it out of the parking lot. Is this a wiseco piston problem? A clearance problem with the exhaust valve? Used to run SPI pistons without issues. Any input would be greatly appreciated. Thanks.

 

[Devilmanak]

Wisecos are forged, SPI are cast. You are not warming the engine up enough, Wisecos need to be good and warm for tolerances in the engine to be correct. Or you get scuffing. Especially in large bore sleds, there is a big difference in piston size from warm to cold.

 

[iride49]

The first time it happened was after a full day of riding. When it happened today, I let the sled warm up for over 15 minutes on the trailer while getting the other gear/sleds ready. So I know the pistons are up to temp before getting on it.

 

[Fiddy]

ditch the wisco pistons they expand to much for the close tolerance go spi

 

[iride49]

Changing to SPI pistons has been the general consensus around here too. Strange how I rode a full season on the wisecos and then lost both of them in the span of about 30 minutes of engine time.

 

[stock suks]

spi

in a snowmobile ive never had luck with siezco pistons, Ive ran them in polaris big bores, cats, and rotax triple mod motors with no luck, have been very happy with the spi pistons in the same motors, they were always warmed up never a cold start and sieze. I had never had problems in quads or bikes with them, but i run spi in everything now