[JW-Tex]

Did you drain the bowls on the carbs? they could be half full of water with the fuel floating on top, when you put the throttle down some other jets may open letting the water in...someone more familar with carbs can provide input. After draining the carb bowls I would hook up a six gallon portable tank with fresh gas/oil (assuming you have to premix) and test the motor, you can then determine if the fuel supply is the issue.

JW