1. Locate the engine. It is located under the front hood of the ATV.
2. Identify the spark plug caps. They are two black caps on top of the engine.
3. Remove the spark plug caps by pulling them straight up.
4. Use a spark plug wrench to loosen and remove the spark plugs.
When replacing the spark plugs, be sure to use the correct spark plugs for your ATV and to tighten them to the proper torque. For the 2001 400 Sportsman, the spark plugs are NGK DR8EA and the torque specification is 14.5 ft-lbs.