Put on rubber gloves. Fill a bucket half full with lukewarm water and add 1/2 cup of detergent. Lay the weed trimmer on its side so that the engine can be accessed.
Locate the air filter cover tab and apply pressure to release the cover. Remove the cover by pulling at an upward angle. This allows for easy access to the filter.
Submerge the filter in the bucket of water and detergent. Remove any debris or vegetation by gently running the filter through your thumb and index finger. Place the filter under running water to remove detergent. Allow the filter to fully dry.
Lightly spray both sides of the filter with motor oil for lubrication. Hold the filter over an empty paint tray and gently squeeze the filter to extract excess oil. Put the air filter back in place and wash off the gloves.
Replace the air filter cover by aligning the slots found on the back of the air filter cover with the open tabs on the back of the weed trimmer casing. Gently press on the cover at a downward angle until it "clicks" into place.
Empty the bucket of water and detergent. Add water until the bucket is half full, and mix in 1/2 cup of detergent.
Dip the scrub brush into the bucket. Use the brush to clean the outside of the weed trimmer to remove dirt and debris. Dry the weed trimmer with the cloth.