A new fuel tank offen has debris in it--it sometimes will take 2-6 filter changes brfore it is clean enough to run without clogging a filter
A reason that it quits at the same spot is because your using fuel at a rate that the filter won't keep up with. Pumping the pedal just lets it run on the accel pump fuel until the carb gets some fuel back in the float bowls, then at a cruising speed it may keep up


Jerry