I thought he'd already bypassed it to the "normal" tank feed that's why i suggested using the "reserve" feed instead as the baffle could have a blockage
what you really should do is get an inline fuel filter and go direct from the carb to the tank baffle with a small inline filter in place, that will eliminate the selector and the separator from the circuit, try both the "normal" and "reserve" feeds...
if it does the same on the trailer you could even just go direct into a jerry can of fresh fuel to eliminate the baffle/tank
which if it continues leaves you with carbs and seals left to test