Dellorto PHVB ‘W’ Needle Conversion Diffuser (262FU)


One of the only long held complaints with the Dellorto PHVB 20.5 and PHVB 22 is its lack of needle tuning ability. This diffuser solves this problem!

The needle controls the fuel flow from the main jet at throttle ranges between idle and full throttle. The diffuser is the tube which fuel must pass through from the main jet to the venturi of the carb to atomise and enter the engine. The job of the needle is to block the diffuser, reducing the fuel flow from the main jet depending on the position of the slide (throttle). As throttle is applied and the slide opens, the needle retracts from the diffuser, allowing more fuel flow from the main jet to compensate for the additional air being allowed into the carb by the slide opening.

Different needles have different tapers, which change how much fuel is allowed to pass through the diffuser at different throttle ranges. Unfortunately the ‘M’ series needle found in the PHVB from factory does not currently have any tuning options…

Fortunately there is a go around! This diffuser allows you to use ‘W’ series needles, for which there are many tuning options! Simply remove the factory diffuser from your PHVB and replace it with this diffuser, allowing you to use ‘W’ needles instead!

Please note that this diffuser does not come with a needle, and cannot be used with the factory ‘M’ needles. To view our ‘W’ needle tuning kits please click HERE


In Stock at Aus Warehouse