Four stroke asp 120 issue resolved

Syphoning may be a problem when the motor isn't running and will fill your inlet manifold but a full pipe will syphon anyway even with the loop in! (Thats how your bog flush works)!. When the motor is running the fuel tank is pressurised so syphoning effect is irrelevant!
I suspect you still have a problem in your plumbing or you dislodged the original problem. The usual suspects that match the symptons are 'low' fuel tank pressure related to the exhaust pressure feed or a fallen off clunk or a crack in one of the brass pipes in the tank.
I use one of those vibration activated fuel pumps which removes the need for pressurised tanks and provides a constant reliable pressure - borrow it if you like dave its not currently fitted to any model,

thanks for the offer john, But had a good day today with lots of spit flights with no issues what so ever (although i may have had my rudder going the wrong way but ill leave the idiots to comment on that). We even had 3 spits up in formation. Warbird heaven