tosatheo, Sounds like it possibly could be a problem with the gas cap vent blocked, loosen or remove gas cap and see if the mower runs better, if it does try to clean the caps vent holes or replace cap. If no better you will have to check for fuel flow to the carburetor. Remove fuel line from carb. and check for flow of gas, if equipped with fuel pump you will have to crank engine to check flow. If no gas flow the problem could be fuel tank clogging at outlet shut off valve/fuel filter,rubber fuel line collapsing/pinched or faulty pump if equipped. If you are getting good fuel flow the carburetor is probably clogged in the ports(needing cleaned/rebuilt)or if equipped with fuel shut off solenoid may be faulty/sticking. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.