Could be that you are flooding the engine while priming it to start. Generally the Low speed needle (the one closest to the engine itself) should be 1 2/3 to 2 1/4 out from fully closed. Set BOTH needles at 2 turns out and see how that works. The clear tube connected to the nipple on the crank-case gets connected to the fitting on the carb closest to it - this is the fitting on the BOTTOM of the carb if the engine is held with the spark plug pointing up.