I have a os 70 surpass mounted in a aircore colt. When it is cold it starts up great and runs pretty good. But after a few seconds at full throttle the engine will start to surge about 300 rpm. I also notice the smoke density changes. I also notice bubbles in my fuel line. The tank is mounted right to the power cartridge so there is no room at all for foam around the tank. Also when I shut the engine off and try to restart it when hot it will not start. I can prime it till fuel is running out of the carb and it wont even try or kick back. I have messed with the needle valve setting and it does it no matter how rich or lean I set it. I also noticed when I bring the engine to an idle it will idle very nice for about 5 seconds then it will start to smoke and u have to move the throttle up to keep it from dying. Where do I start? thanks