Set the Poulan chainsaw on a flat, well-lit workbench. Move the ignition switch firmly into the "Stop" setting. Pull the front-hand guard backwards to disengage the chain brake.
Unscrew the two bar nuts on the clutch cover using the wrench side of the combination bar tool. Remove the clutch cover and take the bar and chain off the bar posts. Separate the bar and chain.
Clean the bar, chain and clutch cover with the brush and rag. Inspect them for any damage, cracks or other problems and replace if necessary. Brush away any sawdust and dirt around the clutch area and the top of the engine.
Unscrew the screws holding the cylinder cover to the top of the engine. Take the cover off and pull out the air filter from its mounting post. Clean the cylinder cover, air filter and the area on top of the engine with the brush and rag. Inspect for damaged parts and replace if necessary.
Unhook the rubber boot from the end of the spark plug. Unscrew the spark plug using the wrench side of the bar tool. Check the rubber boot's metal prong and the wire to make sure they aren't damaged or dirty. Clean or replace as necessary. Screw the new spark plug into the engine.
Brush off the fins of the cylinder cover lightly, making sure no dust falls into the engine. Unscrew the starter cover, on the opposite side as the clutch. Take the cover off and clean it with the brush and rag. Brush off the area around the flywheel and ignition module. Check for any signs of damage and repair as necessary.
Loosen and remove the fuel cap. Dump any old fuel from the tank into the fuel container. Pull out the fuel filter and fuel line from the tank using the metal hook. Pull the fuel filter off the end of the fuel hose. Press the new filter's nozzle into the hose and set them back into the tank's bottom.