The float-valves are #16030. They are pushed up by floats and seals off fuel-inlet from gravity pressure. Otherwise, fuel continues to flow into carbs, fills up bowl and pushes out jets and dribbles down into engine.
While at university, I got my first VF500F for free because guy thought he seized engine. Upon closer inspection, crankcase was completely filled with petrol and engine wouldn't crank or bump-start. Leaky float-valves was culprit. I went back and gave him $500 for it.