Mixture screw leaking

[Mark YPVS]

sounds like two probs to me, the float needle may be worn or stuck so the carb is over filling and the O ring on the mixture screw is letting by, however the fuel should come out the float bowl overflow first not the screw, the carbs may be a bit blocked? so you may need to strip, clean and replace seals, O rings, float needles etc.
Mark