Fuel system problems often cause the engine to stall, so you'll need to rebuild or replace the carburetor if it won't stay running. Our fuel, ignition and compression problems video provides additional tips for troubleshooting fuel system problems.
Some engines stall if the gas cap vent gets clogged. Check your mower's gas cap and clear the vent if it has one. Tuning up the mower engine may also help keep the engine running as you mow the grass.
These repairs may help solve your gas walk-behind mower problem
Rebuild a lawn mower carburetor
A clogged or dirty carburetor causes the engine to run rough or prevents the engine from starting. If you can start the engine using starter fluid but the engine won't continue to run, clogged carburetor jets may be the problem. Clean and rebuild the carburetor using a carburetor rebuild kit if the engine won't start or it runs rough because the carburetor isn't supplying the engine with fuel.
A clogged orifice or jet in a carburetor prevents the engine from getting the mix of gas and air it needs. When the carburetor is clogged, the engine won't start, runs rough or won't stay running. It's usually more effective and cost efficient to replace the carburetor rather than rebuild it.
Tune up a walk-behind mower when the engine runs rough or won't start. You may need to tune up the engine when it vibrates too much or won't stay running. Regular tune-ups prevent engine wear and improve engine efficiency. A walk-behind mower tune-up includes changing the oil, spark plug and air filter. It could also include sharpening or replacing the blade.