I had a play and I think, as you say Grumpy, there was a fuel restriction blokage of some sort. I have a fuel tap and inline filter and removed the filter and it ran just fine. Started and then retarted it many times with no issues.
Its a gravity feed and when I pulled the hose from the carb inlet fuel would only very very slowly dribble out. I used a second piece of hose with no tap or filter and the fuel poured from the hose at any level below the tank level. Very strange. All these tests were done with no fuel cap.
