The gas cap on the tank has a vent in it that lets air in as the fuel goes out. If the vent is clogged, the fuel going out of the tank into the carbs as you drive will create a vacuum in the tank that will nearly stop the flow of fuel.
Checked this out, and the pathway was clear. Thx for the tip, learned something new.
Overall update is the bike is running well after all the voltage checks, switch cleaning, and fine adjustment on dwell and timing. Took a spirited 15 min ride yesterday with no issues, other than petcock leaking on the outlet when the bike it sitting... ordering replacement. Going to try a longer ride today, fingers crossed.
