Sounds like vapor lock to me. Getting more and more common. Fuel used to be formulated to resist that as cars with fuel pumps that pulled fuel from the tank, around hot things, over hot asphalt, would boil the fuel and not be able to pump the vapors. Runs the float bowls low an fuel and you get the lean condition you describe. Today's cars, with pumps in the tank and high pressure fuel systems will not suffer that malady. It's frustrating that we are having to relearn how to cure vapor lock as it had become almost extinct. The new alcohol fortified fuels are even more prone to boiling under heat and vacuum.

You need a pump as close to the tank as you can get it. If it's vapor lock you will fix it. Just buy a cheap electric pump and wire it through the ignition switch. An extra plus is, it makes starting after sitting long enough to evaporate the fuel out of the carb really quick. When you turn on the ignition, it fills the float bowls. No having to crank and crank to get the mechanical pump primed and fuel up to the carb.