How to Winterize your tractor or lawn mower.
By jackssmallengines.com

This will help you get off to a good start in the Spring.
It’s easy to winterize your tractor, lawn mower, or anything that uses a small gasoline engine. The procedure that is laid out here assumes that you will not be using the equipment again for sometime (longer than 60 days).
Lets start with a good clean up. A little soap and water will make the job easier. If you have a pressure washer feel free to use it but take care you do not force dirt and water into bearings that were not designed to withstand that kind of pressure. The high-pressure spray will also wash away any lubricant. After a good cleaning it would not hurt to wax the metal.

The next step is to inspect the deck, deck belts, hangers, and blades. If anything is broken or worn, plan to replace it during this winter’s downtime. If you have the deck off or tractor jacked up, remove the blades and have them sharpened. You can get the blades off by blocking the blade with a piece of wood and unscrewing the blade bolt or nut. Wearing gloves is a good idea especially when re-installing the sharpened or new blades. Check deck belts for signs of wear and replace if necessay so you can make it through the next cutting season without downtime for a belt that you knew would not make it.

If you have removed the deck, now is a good time to lube the tractor. Most owners manuals will point out where, and what kind of lube should be applied. Be careful not to force too much lube into sealed bearings and push the seal out which will allow dirt and debris to get in, causing the bearing to fail. Slowly lube these areas so you can see the lube just seeping around the seal.

Oil Change: Check the oil level. If it’s ok, start the engine and allow it to warm up a little. This will make the oil easier to change and will also stir up the dirt that maybe in the oil pan so that it will come out with the used oil. Stop the engine and drain the oil. Don't forget to replace the drain plug before refilling. If your engine is equipped with an oil filter, change it now. Refill with the proper oil for your engine.

Now for the engine.
Gasoline is very dangerous. Work only in a well-ventilated area, away from any source of heat or open flame!
Start by changing the fuel filter. Clamp off the fuel line between the tank and the fuel filter. Remove the filter by loosening the clamps that hold it and pulling it out of the hose. Be careful to catch any gasoline that may spill. Always replace the hose that is between the filter and the carburetor. Notice that the filter usually has barbs on it. These barbs tear the inside of the hose when the filter is removed. A piece of hose could enter the carburetor and cause real problems.
Remove the air filter and pre-cleaner. (Be careful not to let any debris fall into the carburetor.) Clean or replace them as necessary. Reinstall the Air Cleaner.

Next, let’s prepare the gasoline itself. I have often read that gasoline is only good for 90 days. There are 2 problems with this. The first is it is 90 days from date of manufacture not the date you bought it. The second is that gasoline is volatile in air, meaning that it evaporates quickly. Gasoline should be stored no more than 30 days without treatment and that includes the gas in your machine. So we must prepare the fuel system to sit out the winter without damage. There are 2 schools of thought here. One is to drain all the gas leaving the fuel system dry for the winter. The problem is that water can collect in the system because of condensation. Water will cause more damage than the gas will. Also by removing the fuel, the gaskets and seals in the carburetor can become dry and brittle causing carburetor problems. But leaving the fuel system full can cause just as much trouble due to stale gas and the solids that collect at the point of evaporation. The latest thinking for storage is to fill the tank with gas that has been treated with stabilizer. The stabilizer keeps the gas fresh and helps prevent the build up of deposits. A full tank keeps condensation from happening.
Note. After you fill the tank with stabilized fuel you must run the engine for about 10 minutes so that the treated fuel enters the carburetor.

We are almost done. Park the tractor where its going to sleep away the winter because after the next two steps we don't want to start it again. If you will be using the tractor to push snow or something then stop here.

Now, remove the spark plug, put a teaspoon of engine oil into the spark plug hole. Replace the spark plug with a new one(s). With the spark plug wires disconnected crank the engine over a few times to spread the oil inside the cylinder(s). This will coat the cylinder(s) wall, and reduce the chance that condensation will rust the cylinder(s). If it is possible to turn the engine over by hand, do so until you feel the compression stroke. This closes the valves and prevents moisture from getting into the engine.
Remove the battery from the unit and store it away from any ignition sources in a cool place but a place not likely to get below freezing. Charge the battery before storing it. Also, make sure you keep the tires inflated over the winter.