The PHBN needle valve was not seating correctly, meaning that the fuel bowl was over-filling, with fuel overflowing out of the carb throat.
The primary problem was due to a worn needle valve. Previously the only solution to this, would be to buy a new needle valve.
However I have developed another method. This is based upon the principal: If the valve bush is reseated by a few microns, the needle valve will regain full contact.
The method I came up with, removes such an insignificant quantity of metal...... there is effectively no change to the float cutoff specification, and it will not prevent the use of a new needle valve in the future.
Bamboo BBQ skewer Metal polishing paste Dremel type tool Cotton bud stick Aerosol cleaner
Cut the pointed end off the skewer to about 50mm Clamp in the Dremel type tool. Set the speed to about 15k Run the point of the skewer in the bush, allowing it to form to the bush diameter. Coat the point with a very small quantity of metal polishing paste. Polish the bush for approximately 10 seconds. Take a cotton bud stick..... remove some cotton to allow it to enter to the bush, and rotate to clean off. Repeat using the other end of the cotton bud stick. Blast through with aerosol carb cleaner.
An entirely safe procedure, that could buy you time to get a new needle valve..... or possibly obviate such a need for the foreseeable future.