I have a 2006 Ski Doo MXZ 550 Fan that blew a piston which then tore up more of the motor. I have a quote for about $2000 to repair.
This happened after I got gas in Holderness. It seems that ethanol gas/water is the problem.
FYI Here are 2 products I have heard of that may help with these issues:
http://www.k100fueltreatment.com/
http://mystarbrite.com/startron/
A friend of mine uses K100 in all his sleds and in his boat during the Summer.
Smitty1