I'd look to see if you have any bubbles at all, when the tank is full. Look at the fuel line from the carb. If you have any bubbles, pull the motor and get some high temp silicone and seal the back plate, the carb base, and your pinch bolt. I do this to all my engines as a pre-caution anyway. My pressure line in my MTX3 is about 4 inch's long, and my fuel line is around 3 inch's. I've ran the Mugen x12 engine, OS-TR, and now the Sirio modified by Mernan.

Hope that helps.