I ran into a similar problem with gas pouring into my air box on a 2003 Rubicon 500. This was AFTER rebuilding the carb. My first thought was the float needle was faulty and sticking, but after (2) times of disassembly and determining that was not the problem, I figured it out! I installed the carb drain line backwards causing I guess a vacuum or venting issue. Air can only travel one way through the in line valve which I'm guessing to keep water from entering the carb while driving through creeks etc..? Anyways, flipped it around and no more gas leaking issues. Purrrs like it should.