Sounds right if you had a gas leak. If gas was leaking into your cylinder, it would end up falling out to the pipe. There could be a pool of old gas that is still in your pipe that will not end up burning but will blow out your back side.
Just take it on a good run. If it is still spitting gas, then maybe your reeds are not closing properly and excess gas is getting in and not being burned in the cyl, again falling thru the pipe and blowing out.