I answered in your other thread. Now I see what you're trying (wrong) to do. I had the 60 size Dumas Swampbuggy and a scratch built 40 size. I made it easier on myself by having the engines facing forward. Guess that's why the plan designers did it that way also. As one poster mentioned, the engine will stay much cooler and you can then use the electric starter. Turn the engine 180 and your life will be in better sync with the universe.

Forgot to mention, you need to put fuel tubing over the rudder rod detent screws. Metal to metal rubbing will cause RF interference.
I'm surprised the engine will run at all -- The tank outlet should not be more than 1/2" below the centerline of the carb unless you have a pumper on the back of crank case.