If memory serves me correctly the 2601 has a tank vent at the of a piece of fuel line sticking up next to the engine? Also, if the fulcrum height in the carburetor is not set properly it will leak gas out of the carburetor as presure in the ank builds from buoncing around in the back of the truck, or as the temperature rises the fuel expands. If the diaphragms in your carburetors are old and stretched they can also keep the fulcrum open will the engine is not running.
Mr Wrench. do you have any other ideas what would make one leak? I have rebuilt the carbs and reset the fulcrum and we still have the leaking problem. New kits. We are thinking about new carbs. I have pressure tested the carbs and no leaks. It almost acts like the tank is pressuring up too much for the inlet needle to hold. The tank vent on the echo lets air into the tank only.