Engine sputtering... too rich...but with the fuel tank mounted that high, it will syphon fuel into the engine. Get a litrtle 3/4 ounce or one ounce shampoo bottle from the motel... the kind you get each night you stay... drill two holes in the cap for the tubes, and put in a brass or plastic tube for the engine fuel [that ends inside at the rear right hand side of the bottom of the bottle, and the engine end stops about 1/4" outside the tank, for the fuel line to attach.] and another tube for the vent [with one end at the top inside of the tank, and the other end which ends above the tank outside.] Mount the tank center line level with the center of the engine crank case. When all that is done, remove the tank and put some silicone caluk or 'Goop' on the bottle threads and screw the cap on, then put some caulk or 'Goop' on the cap where the tubes come out. Adjust the fuel pick-up line to the bottom right, and the vent to the top. Let that dry for a day or two, then mount the tank so the fuel pick-up line is to the right side of the bottom and the vent is to the top, and the center line of the tank is level to the center of the crank case. You might have to cut a hole in the wing and build a box there for the tank. Sometimes a smaller, shorter tank will fit between the wing and the engine. I think that's why the metal tanks we use to buy had the fuel tube come out the top of the tank. You could do that with the plastic bottle too. Both the fuel and vent tubes could come out the top. We use to take a 1/2" piece of fuel line and cut it at a 45 degree angle and stick that on the vent, slant facing forward to catch the wind and pressurize the tank a little, to help the fuel to flow to the engine more steady. Good luck !!