I have not read all the responses to your problem. However here is what you need to do.

1. Pull the tank.
2. Pull the stopper and replace the fuel pickup line. Ensure when you cut the new tubing that you cut it with an X-acto knife. DO NOTUSEWIRECUTTERS!!
3. Re-install your stopper and make sure it is snug. Make sure the clunk does not touch therear aft sideof the tank when it is held upright.
4. Replace the external lines using an x-acto knife to cut the lines. Roll the fuel tube under the knife for a straight cut.
5. USEFOAM around your tank, and re-install your tank and hook up your lines.
6. Balance your propellor. (excessive vibration causes foaming inside the tank which will lean your mixture.)
7. Run your engine and check for bubbles.

All the above take into account that nothing is wrong mechanically with your engine. Make sure your carb fuel fitting is snug. Go fly.

Glenn Williams