My thought is that it is temperaly running out of fuel.
Have you herd of the ball plunger fitting just out of the tank going bad? Took the line out this morning and cleaned junk out of it. I also removed a little bit of junk out of the screen at the carb. New filter. Took tank out of boat this winter so all new gas. I have taken all fuel lines apart and blown air through them. Which part of the carb would case this prob.? Runs great then dies.