Well one thing I see right off of the bat is that the tube on your vent side (the one that goes to the muffler) should point up towards the top of the fuel tank, not the bottom. You need to have the end of this tube as close to the top of the tank as possible. When you fill the tank you will only be able to fill it as full as the end of that vent tube, when the fuel level gets to that tube it will start blowing out the vent line. This is why you want it at the top of the tank, so the fuel overflows out the vent tube when the tank is full. See diagram.

Hope this helps

Ken