Get out and puul the gas cap as soon as it stops. Could be the vent tube from the fill neck kinked or plugged up
Check the sock in the tank it may not be letting enough fuel through.
The Brown Duster I am working on. The new fuel pump would not pump fuel at all. It was the arm on the pump was incorrect. Not getting enough travel from the eccentric.
Everything mentioned above also. You need to determine if it is spark or fuel