I dunno about your bike, but on some carbs mixing up the float bowls can be a problem...
On my bike (400F), each carb body is numbered (1, 2, 3...) and the bowls should be mounted with the drain plugs to the outside (1 and 2 mounted to the left, 3 and 4 to the right when seated on the bike).
I'd guess they got FUBAR'd at the last carb cleaning and that another carb's bowl has a drain plug facing the wrong way. Then again, you might have a 1 or 2 carb switched to #4.
HTH...
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