O/T 2-stroke trimmer sucking air

It starts and runs well at first, but then bogs and dies as more and more air bubbles start coming up the fuel line. You can see the bubbles in a section of clear fuel line. The intake end of the line is well covered by fuel in the tank.

Carb has been been cleaned with solvent and fishing line, all tiny passages clear, diaphragm and gaskets appear to be good, float valve works, fuel intake has been removed to eliminate starvation from the equation.

Spark and compression are no problem, as evidenced by good running at first, but what could be doing that in the fuel supply? Any advice gratefully accepted, thanks in advance.

R

My trimmer did the same thing and I serched for a problem. I found the fuel line had a hair line crack causing it to suck air. The crack was so small you could hardly see it from just looking at the line.

Just a thught
John