well, you need to rebuild them as parts are probably dried and shrinked thus allowing gasoline to bypass float needle and excess fuel from float bowl leaks into airbox when engine is turned off. additionally it also means that your fuel tap on fuel tank is leaking too because if it was good excess fuel should not flow into carbs because it closes fuel automatically when engine is turned off (unless someone changed the automatic fuel tap for manual one).
it would also help to tell us what kind of bike you have... given that you didn't make to choose the right category for your post.