check compression because you probably need a new top end
Inspect clutches for wear, ensure bushings on weights are intact, ensure weight bolts are not worn, inspect clutches for play and replace fiber bushings accordingly. might as well inspect belt for threads or cracking while your down there
pull chain case cover check for damage, wipe clean, reinstall cover and refill with synthetic fluid.
Pull exhaust valves check for torn bellow, damage to blade/shaft, clean thoroughly and ensure top nut is torqued to 16 foot pounds, red loctite never hurts. make sure gasket is completely removed and reinstall valve with new gaskets.
check front end bushings/endlinks for damage or play ensure everything is torqued properly
check skid and put a wrench on every bolt/nut, grease zerk fittings, check idler wheel bearings, track tension.
Its very important to me that i park my sled in near perfection shape so next time the snow falls i'm ready to ride. This list could go on and on
GL