If you have an engine that runs and stops, it could spell disaster and the problem
has to be solved.
Try my way of doing it.
Now here it is. First remove the fuel tank from the plane. Wash out the tank with
methylated spirits or petrol. Check the fuel line tubing from the clunk to brass tube on the cap.
It might be blocked, or it might be cracked sucking air when the fuel level has dropped low.
If necessary replace it.
Re-assemble the tank. Now check your tubing lines for the feed, filler as well as the air vent.
Some guys use only feed and air vent lines.Discard old tubing and replace with new tubing
Make sure to mark or label the lines, so that you wont have to guess which is which,
when re-installing the tank.
Before i install a fuel tank i do the following.
I pressure test the tank and lines by inflating it slightly with a bicycle pump and valve to stop the return of airflow. listen if i hear any air is hissing out, and then submerge the tank and tubing
lines in the hand basin with water, in the bathroom. Air bubbles will reveal all.
The cap must be tightened down properly or fuel will leak into the tank compartment.
You will be surprised what vibration can do to your fuel system.
I install extra foam padding around the tank to absorb vibration. This will cure a fuel foaming
problem if you had one.
Next time a tip on the carburetor.