mrcoolpop,

take apart the fuel tank and test all the tubing. The best way to do this is put a fuel dot (or a screw) on one side of the line, hold the whole line in a bucket of water and blow as hard as you can on the other end. If there is any leak you should see bubbles. They do the same with the other end (the one through which you blew first) clogged.

Once all the lines are tested and you are sure there are no leaks, assemble the tank. You may use a standard or bubble-less clunk and then pressure test the tank the same way.

When installing the tank in the airplane, use as much foam padding as possible to isolate the tank from vibrations.

See whether you can lower or raise the tank to the centreline of the carb. It is not very critical that you match the centreline exactly but it needs to be close if you model allows it. Ensure that you connect the tank correctly i.e. carb line to carb and vent line to muffler. See whether your engine has the same problems after this

If all else fails, use a Sullvian flexitank on the link below.

http://www3.towerhobbies.com/cgi-bin...?&I=LXFU64&P=7

If you are having foming problems, this tank will likely resolve them as it is a soft tank and will absorb vibrations. You can also try the bubble-less clumk sugested by CGR.

I just had problems with a 55ax not running properly just like yours though I didnt note any bubbles. After I put in the flexitank and clunk and a club expert tightened my head bolts, the engine runs fine. Dont know which of those was the problem, but if it runs dont test it.

Best of luck resolving the problem

Ameyam