I have the same problem with my OS 20 R/C. If it's spitting fuel from the carb that usaully means to much fuel is getting in. One thing I found was that if the tank is a little to high or even with the carb, fuel will just trickle in and fill the crank. I gad to take the plug out and spin the prop. The other thing iis mmake sure your idle screw is set right. close all the way then back off 2 to 2 1/2 turn and check that the whole is half open, or closed depending how you look at it. I also found the needle valve set at 2 turns out is a little heavy. Start at 1 1/2 turns and work from there. Good Luck.