I did undo the brass screw on each and drain them down over this winter and what came out was clean as a whistle. But they could be knackered yes.
One thing I noticed that I didn’t like was the mixture screws turn really easily - so easily I don’t know how they don’t move under vibration: I don’t know if that means the needle is gone, the carb hosing they screw into has gone, the little spring on each on has gone- or all three…
I will try taking them into 1 1/4 turns and see if improvement.