" I drained the carbs, made a B-12/Techtron mixture, pulled the fuel line put it in the mixture bottle,turned the key, and it sucked it up just fine.. started it up, it ran ok at idle, I can see it drawing down the mixture as it ran, so it seems all is OK with the fuel system"
This was bypassing the petcock, and you said it ran fine...until you hooked the hose back to the tank.