Check to see if the line inside the tank that goes to the muffler is not pressed up against the inside of the tank. Meaning the fuel line that is bent up, is not being plugged by the inside of the tank, you must have a little space between the line and the tank.

Also, are you sure you don't see any fuel going into the carb. That line that goes from your needle valve to your carb, is there fuel in there or not?

Also, check to see if the line that has the clunk on it is sitting in the fuel. I know this sounds dumb, but sometimes that clunk gets jammed in that tank, the line gets bent and then no fuel pick up.

The last thing is that I have never had a tank with a filler. I always plug that third tube and use the line that goes to the needle valve, to fill. You might try that too, cause there could be something wrong with that filler tube.

See if that helps. Good luck