silicon

I have a Duratraxx thunderquake, and i have a problem where the gas after about 5-10 mins will suck up into the fuel line and no gas gets to the carb. as it sit you can see the gas slowly crawling back to the carb, and then it will run for about 5-10 mins again and do the same thing. Has anyone seen something like this and have any ideas? I have replaced the fuel line and have tried to move the fuel line away from any heat, but no luck, it seems like a vapor lock issue but i don't have any idea how to fix it!

please help!