Small Engines (Lawn Mowers, etc.): lawn mower keeps cutting off, briggs straton engine, delivery problem

Question
I have a lawn mower with a Briggs & Straton engine. It's pretty old but runs well. It keeps on cutting off after running for about one minute. It starts with no problems. The one thing i noticed was that after the engine is started, the rubber purge button starts to suck inward like being pulled by vacuum inside. Is this a fuel delivery problem? Thanks in advance.

Answer
Check the gas cap. If the vent is broken the tank cant breath as the gas is being used. it creates a suction in the fuel system cutting off the fuel flow. you could try letting it run and as the mower starts to shut down unscrew the cap halfway to see if it returns to normal.