When you say the bubbles are from the tank to the needle, I'm assuming they continue from there to the carb. (Right?)

Did you tighten the stopper screw down really well? If it's a bit loose, you could be sucking air there. It's also possible that you have a small pinhole in the line where it connects to the tank. (It wouldn't necessarily leak fuel.)

A water test isn't a bad idea if the tank and lines are easily removed. Plug all but one line, hold the tank and as much of all the lines as possible under water, then blow into the one open line to pressurize the tank. Hold that pressure for quite a while and watch for small bubbles. (You can do it out of water too, you'd want to pressurize the tank, then wait a few minutes. If the tank maintains pressure, there are no leaks.)

Good luck,
Dennis-