I had a problem with the float chamber emptying. Spity run like a dog but ticked over ok.
checking the float chambers and found the front was very low in fuel. Check the pump pressure at the small rubber pipe that connect the float chamber to the steel pipe that goes between each float chamber. Pressure was ok so I changed the float jet and seat, but still the same problem.
So I removed the pipe with both short rubber pipes connections attached and blew down the pipe backwards (front carb to back carb ) all OK. Then I blew down the pipe from the other direction the way the petrol flows and it was blocked.
I cut the rubber pipe open along it's length and found the inner coating of the pipe had broke away and was a flap acting as a one way valve. So when inserting the pressure gauge into the pipe it pushed open the flap.
Always expect the unexpected with a Triumph