If it works for a few minutes before going out, it's not a fuel line outside of the tank. Could have something to do with the tank assembly. Make sure it's put together right with new fuel lines.

Sounds like it's just not adjusted properly. It is more than likely running too lean...Ask an experienced flyer at your club to help you adjust it. When you lean it out for peak RPM, back it up (rich/counterclockwise) until you hear a noticable drop in RPM. Always run it on te rich side...