Carburettor -YSN PHBH 28 BS- CS=34mm – with vacuum/oil connection

The YSN PHBH 28 carburettor is almost identical to the original in all details. With the manufacturer YSN we have a very good and reliable manufacturer at our side, who continues to produce the legendary carburetors for us. The quality is absolutely comparable with the Italian original and the parts are also 99% interchangeable. Only the gas slides are guided by a slightly longer centering pin in the carburetor. If Dell’Orto gas sliders are to be used, this pin in the aluminium casting can be simply taken back a little bit.

A big advantage of the PHB carburettors is their simple and good tunability as well as their insensitivity to weather changes. The PHBH 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 also quickly lead to problems.

On most scooter engines, the following basic fuel mixture has proven to be a good starting point for the PHBH series:

• mixing tube: AV264
• needle: X2 or X3
• side jet: 55
• main jet: 120-145
• slide: 30 (rich) or 40 (lean)

If problems with the fuel supply are suspected, it is advisable to convert to a larger float needle valve (#250).

BS Carburettor = adjusting screws in suction direction left