Small Briggs & Stratton vertical-shaft lawnmower engines have air filters to clean dust and dirt from the combustion air. Briggs & Stratton mower engines either use a foam filter or pleated paper filter. Eventually, dust and dirt can build up in the filter to a point where the engine runs rough for lack of air. Air filters should be checked frequently and cleaned as needed during the mowing season.
Things You'll Need
- Flat-head screwdriver
- 5/16-inch socket wrench
- Old rags
- Compressed air source
- Small bucket
Foam Air Filters
Check if your Briggs & Stratton lawnmower engine uses a foam air filter. On most models using a foam filter element, the flat filter housing is oriented horizontally and is located to the left of the spark plug as you face the plug. The cover of the filter housing is held down by a slotted screw in the center that you access from above.
Undo the filter housing cover hold-down screw with a flat-head screwdriver. Lift off the cover. Lift the foam filter element out of the filter housing. On some engine models, the foam filter element has a metal or plastic spacer in the middle. Remove the spacer and set aside.
Wipe surface dirt and dust off the foam filter element. Pour a small quantity of gasoline into a small bucket and wash the foam filter element in the gasoline, squeezing it to get all the dirt and dust out. Allow the filter to air dry. Alternatively, wash the filter element in hot water with a generous squirt of dish liquid added. Rinse in clear water until suds are gone. Squeeze out excess water. Allow to air dry.
Pour clean motor oil onto the foam filter and squeeze it to spread the oil throughout the filter. Wrap the foam filter element in an old rag and squeeze it to remove excess oil.
Reinstall the foam filter in the filter housing on the engine. If your filter has a metal or plastic spacer, reinstall the spacer. Place the cover back on the filter housing and tighten the cover hold-down screw.
Pleated Paper Filters
Check if your Briggs & Stratton lawnmower engine uses a pleated-paper air filter. On most small engine models with paper air filters, the filter housing is oriented vertically and is located to the left of the spark plug as you face the plug. The flat rectangular cover is secured at the top by a screw.
Undo the cover screw with a flat-head screwdriver or 5/16-inch socket wrench. Tip the air filter cover toward you and lift it up from the tab slots that hold the bottom edge in place.
Pull the air filter element from the filter housing and inspect it. The rectangular filter element is made of pleated paper backed by wire mesh and has a rubber edge. If the filter element is not damaged or fouled with oil, clean it by blowing dust and debris from the filter pleats with compressed air. Gently bend the filter to open the pleats as you blow air over the filter’s front and back.
Replace the filter element with the wire mesh side toward you and the paper pleats facing inward. Line up the tabs on the filter cover’s bottom with the tab slots in the filter housing, swing up the cover and tighten the cover screw.
Tips & Warnings
- Replace the foam or paper air filter elements with new ones at the start of each mowing season.
- Some Briggs & Stratton mower engines use a cylindrical foam or pleated-paper filter element. Clean these in the same manner as flat elements.
- Gasoline is flammable. When using gasoline to clean your foam air filter, work outdoors in a well-ventilated location away from the mower and away from flame or heat sources.
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