Next up is fogging the motor. The crank and bearings are high carbon steel, and that rusts in about 20 seconds when exposed to moisture. Considering that those bearings spin 100-150 times a second and could leave you in the woods on a cold night, and cost a grand or more to fix, take the time to fog them. 

Fogging an engine is easy. Take out your air intake filters, start up the sled on a stand, and spray fogging oil into the carbs/injector bodies a little at a time. It will choke down the motor, so take it a little at a time and give it some throttle. Once there is a lot in there, I start with an increasing amount of fogging oil and increasing throttle until I load enough oil into the motor to choke it out at wide open. 

I am of the mind that I like to put oil down the cylinders and ports to the point that the crank bearings are partially bathed in oil, and occasionally when I walk by I will pull it over and give the bearings a bath. That is fine, but you need to still fog it, or the piston wrist pin bearings will be left high and dry. You also want to keep up on pulling it over, snowmobile oil is fairly thin (especially at summer temps) and will run off of the parts at some point. Fogging oil is thicker and stickier, and probably a better solution if you are convinced that it is reaching all of the parts. The 92-97 XLT 600 motor comes to mind with the second clutch side bearing that is always dry, and always blowing up. 

Corrosion resistance comes next. Pipes like to rust and aluminum engine parts like to oxidize and get ugly when stored in moist places. My answer to this was taking a mixture of oil and a little kerosene and spraying it through an old paint gun. I would hit the engine, the pipes, the skis, the rails on the suspension, and anything else that corrodes. 

Mice are a constant problem. They get in the exhaust and air box, and you really don't want them chewing on wires. I put steel wool in the exhaust pipe, and cover air box entry points with something hard that will keep them out of there. As far as keeping them out of the belly pan, some say to use mothballs, some say no. I say go a step farther and use a little D-con poison pack too. It is cheap insurance. 

You will want to wax your hood, and maybe use a protectant on the seat. The seat protectant is a mixed proposition, it protects, but it also makes the seat slippery next year. Some of you have related stories of unexpected dismounts as a result of some Armour-All on the seat. The slippery surface + inertia path apparently has lead to some surprises. Use some discretion there. 

A cover that breathes a little is a good thing. In an outside storage environment it will keep the sun from rotting the paint and the seat, but still release moisture. It will also help to keep the paper wasps out of your hood. One thing that you don't want is a cover like a blue tarp that holds in moisture. The moisture from the daily warming and cooling that makes dew, also makes dew under that tarp, which traps it, and it will rot anything under it. 

The next item is to get the track and skis off of the ground. I put the skis up on pieces of wood, and do the same thing with the track. Ideally the back would be suspended and the track off of the ground, and the suspension extended at rest. That is great, but don't forget to put a smudge of grease on your shock shafts. You don't want those rusting. 

Beyond all of that, don't overlook regular maintenance. If you broke something over the winter, get that sled to the dealer. The problems are fresh in your mind, and the dealer is absolutely starving for work right now. It is better than waiting until December, when you don't remember all of the stuff that went wrong, there are literally 60 sleds ahead of you at the service door, and you will miss a trip to the UP waiting to get stuff fixed or for parts on order.