Fuel tank wont vent..need help

[Deezymarquez1]

I just picked up a grom clone 125cc, runs good but had trouble starting it the other morning, when I checked the fuel I heard a vaccum sound, and then it started fine..rode to work and since i knew of the problem I opened the gas cap and it literally popped at me since the day had warmed up, do I have a bad gas cap that isnt venting or Is there an issue with my carb?