A big advantage of the PHB carburettors is their simple and good tunability as well as their insensitivity to weather changes. The PHBL shows quite fast and clearly if the mixture is too rich or too lean. A Mikuni or Keihin carburettor usually runs surprisingly well, even if tuned too lean, which unfortunately can quickly lead to a problem.
If problems with the fuel supply are suspected, it is advisable to convert to a larger float needle valve.
BS carburettor = adjusting screws in suction direction left