Carburator kit -YSN PHBH 28 BS, rotary valve- Vespa PX (1984-), Cosa, T5, LML Star/Stella

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

Replaces the factory fitted standard carburettor and allows for better engine tuning.
The factory fitted Dell'Orto SI carburettor is suitable for demanding engine configurations (e.g. The Dell'Orto SI carburettor is often difficult to tune for demanding engine configurations (e.g. with resonance exhaust) and power ratings above the 16kW mark.

BENEFITS PHBH
The PHBH carburettor type offered in this kit is much easier to tune.
The conventionally designed PHBH round slide carburettor responds clearly to changes in fueling conditions and quickly results in a smooth and easy to drive setup. This is also very stable under changing weather conditions, which makes this carburettor type especially suitable for beginners and all-weather drivers.
Another big advantage of this set is the longer intake travel.
This dampens any blow-back in the intake tract and ensures a clean throttle response even at low engine speeds.In addition, the torque curve often also benefits from the longer but larger intake cross section.

frame connection
The set can be driven to the frame with the standard intake hose without any problems using the supplied intake funnel. The intake noise is therefore only slightly louder than that of a standard carburettor.

QUALITY
The YSN carburettors included in this set correspond in almost every detail to the original Dell'Orto carburettors. The quality is absolutely comparable with the original Italian 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 can be taken back in the aluminum casting simply a little bit.

CONTROLING
The nozzle setup of the YSN carburetor is already roughly pre-tuned for the use on a Vespa engine. Normally it is sufficient to adjust the main jet to the own engine. Here a low-priced main jet set for tuning is offered. Basic rule: tuning from grease to lean. This means that a deliberately too large main nozzle is chosen with which the engine starts to stutter when accelerating. Then the main nozzle is reduced until the engine just doesn't stutter any more when you drive full throttle. This corresponds then to a main nozzle size which means maximum safety for the cylinder. For the best power delivery the mixture can be further reduced from this point by using a smaller main nozzle. As a rough guide for rotary vane engines: Main nozzle size 120-135, membrane 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 slightly 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.