Snowmobile Repair: 1997 ski-doo touring sle 500, lean mixture, piston rings

Question
My 1997 ski-doo touring sle 500 was stored for 5 years, It was just parked with 1/2 of gas and never sumerized. I took it out at the start of this year. I had some trouble getting it started, I put some gas in the clyinders and it fired up.
It ran good for about 100 miles and than it one day it staled out on the side if the road, I got it towed back. After that I cleaned the carbs and bought new plugs. It starts after 5-6 pulls, but now it is running really slow like 60 km/h top speed I think it is only running on one clyinder,
So my question is can piston rings blow from not summerizing for 5 years, Is my problem rings or do I need to bore it out and buy a whole new bigger piston. and one more question what does the head on a 1997 ski-doo touring sle 500 need to be torqued to?

Answer
Hello Kyle,

 Sorry for the delay in my response. The engine being burned up is very possible. The reason for this is, the jets in the carb get clogged with gum and varnish and provide a lean mixture to the engine, a dangerously lean mixture. But, it's always better to thoroughly look into other possibilities before tearing the engine apart. I would start with checking for spark, it's always possible that only one plug is firing. If the spark test checks fine, then I would recommend removing the heads, and then cylinders for inspection. Start with looking at the cylinder walls for wear. If they are scored, you would have two options. One would be to install new sleeves, which fortunately standard on Ski-Doo's. The cost about 100 each. Other than that, an overbore would be necessary and larger pistons. If the cylinders look fine, your best bet would be a complete top-end rebuild kit. You can get one for very cheap here;  http://www.denniskirk.com/jsp/product_catalog/Product.jsp;jsessionid=C3YA4ZGPBQC...  .

Also, here are  the over bore kits: http://www.denniskirk.com/jsp/product_catalog/Product.jsp;jsessionid=C3YA4ZGPBQC...    .  Also, the largest over bore kit:  http://www.denniskirk.com/jsp/product_catalog/Product.jsp;jsessionid=C3YA4ZGPBQC...  .  Head bolt torque would be 21 ft. lbs. Hope this helps you. Let me know if you have any other questions. Good luck with the sled! --Arcticatman