Small Engines (Lawn Mowers, etc.): 5 HP Briggs motor, hp briggs, fuel tank cap

Question
I have a 5hp Briggs motor on a kids yard cart. It idles great, throttle response is super but while riding it after a few minutes it just quits. You then have to put it on choke to get it to start but then again it runs fine and after a few minutes it does the same thing. I have replaced the diaphram which looked bad, new spark plug, sprayed carb cleaner through it, cleaned the gas tank and strainer but it hasn't helped. Please give any suggestions you have. The kids really want to ride it. Thanks so much, James

Answer
James
Problem: Engine starts easily but dies after a few seconds.
Possible causes:

Fuel tank is empty or shutoff valve is closed, or fuel line or fuel tank cap vent is clogged.
Carburetor is overchoked.
Carburetor is improperly adjusted or needs service