Carburator kit -YSN PHBH 30 BS, rotary valve- Vespa PX (1984-), Cosa, T5, LML Star/Stella

Complete PHBH carburetor kit including intake manifold and small parts for Vespa PX and similar.

Replaces the factory carburetor and allows better tuning of the engine.
The factory Dell'Orto SI carburetor is often difficult to tune for demanding engine configurations (eg with resonance exhaust) and power above the 16kW mark.

ADVANTAGES PHBH
The PHBH carburetor type, as offered in this set, is much easier to tune.
The conventionally designed PHBH round slide carburetor responds clearly to changes in jetting and quickly leads to a setup that is easy to drive. This is also very stable in changing weather conditions, making this carburetor type suitable for beginners and all-weather riders.
Another big plus of this set is the longer intake run.
This dampens any blow-back in the intake tract and ensures a clean throttle response even in the lower rpm range. In addition, the torque curve often benefits from the longer but larger intake cross-section.

FRAME CONNECTION
The set can be easily driven by the supplied intake funnel with the standard intake hose to the frame. This makes the intake noise only minimally louder than a stock carburetor.

QUALITY
The YSN carburetors included in this set correspond almost in all details to the original from Dell'Orto. The quality is absolutely comparable with the Italian original and the parts are also interchangeable to 99% 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 aluminum casting can simply be taken back a little.

OPERATION
The jet setup of the YSN carburetor is already roughly pre-tuned for use on a Vespa engine. As a rule, it is sufficient to adjust the main jet to your own engine. Here a low-priced main jet set is offered for tuning. Basic rule: Tuning from fat to lean. This means that a deliberately too large main nozzle is selected with the engine starts to stutter when accelerating. Then the main jet is reduced until the engine no longer stutters as soon as full throttle is applied. This corresponds to a main jet size that provides maximum safety for the cylinder. For the best performance, the mixture can be further downsized from this point via a smaller main jet. As rough guide values for rotary vane engines: Main jet size 120-135, diaphragm engines 125-145.

We offer the set in two versions

• for engines without separate lubrication (up to approx. 1983)

• for engines with separate lubrication (from approx. 1984)

The sets differ only minimally in the scope of delivery. The set for engines with separate lubrication contains a plug to close the hole for the oil pump drive. The oil pump cannot be used.