My Craftsman Push-Mower Engine Won't Start With the Air Filter On

Check Air Filter

• The air filter sits on the right hand side of many Craftsman push mowers, usually just above the fuel tank and the carburetor. A long screw mounts the air filter box to the engine. Remove this screw and the box to access the air filter. Other push mowers will use an air filter box that is locked into place without a screw and may be twisted to unlock them from the engine. Open the box and remove the foam element of the filter. If the air filter is dirty, knock off the dust with your hand. Don’t use gas to clean the air filter and don’t oil the filter.

Replace Air Filter

• If the air filter is too dirty to clean it will should be replaced. Craftsman recommends replacing the air filter after 100 service hours or at the beginning of every season, whichever comes first. They also recommend replacing the filter more frequently if the mower is continually run in dirty, dusty conditions. In these conditions the air around the filter box is dirtier than usual and forces the filter to work harder, and invariably it clogs faster.

Dirty Carburetor

• If replacing the air filter doesn’t solve the problem, the carburetor inside the engine may have gotten dirty or damaged. A dirty filter can damage the carburetor and engine because particles may sneak past the filter and into the engine. Often, the inlet valve’s filter on the carburetor will be blocked with a piece of grass or dirt. If these particles make it further into the cylinder, they can scour the sidewalls and do permanent damage, so it’s best to replace the filters regularly.

Clean the Carburetor

• After the air filter is replaced, the carburetor may get too much air and the engine may not start. With a new filter the balance between the air and fuel mixture may be wrong, which will require a cleaning of the carburetor and fuel system. The carburetor should be removed from the engine and disassembled. The parts will need a thorough overnight soaking in a carburetor cleaner bath to remove any trapped particles of grass or dirt.