Took the bowl off the carburetor to check the float needle, turned on gas valve at carburetor and minimal gas flow.
Opened the drain valve on the potato and very little gas flow so I then thought the vertical accessory screen above the potato was clogged. Siphoned as much gas from the tank as possible and then removed the potato. Both the vertical screen above the potato and internal vertical screen hospital clean. All this time I knew this was not a air vent in the gas cap problem because the vent hole has always been clean.
Puzzled by this I re-installed the potato, gas line, carburetor float and bowl then filled the tank. Opened the valve at the potato, valve at the carburetor and opened the valve below the bowl. Full flow and lots of gas coming out.
Still in a quandary of what caused the initial lack of gas flow I went to re-install the passenger side of the seat and accidentally looked at the underside of the seat and found the problem.
A past owner who had the Coupe reupholstered went to the trouble to have faux leather applied under the seats and one can easily see a circular pattern from the flat gas cap indented into the leather. Apparently conditions were right for the leather to be pressed onto the gas cap and a vacuum formed where air could not enter the tank. I have since drilled a second vent hole and installed a tiny plastic riser at the top of the cap where the leather cannot press on the cap. Took a ten mile ride and all is well. This was a first for me!
