Throttle slide -DELLORTO SI24- Vespa PX200 (Typ 8492-4)

The SI carburettor slide valve has some special features.

Cutaway

All slides have in common the small central cutaway at the beginning of the slide surface. This is important for the throttle response on the first millimetres of slide stroke. If the angle of attack of the cutaway is changed here (filing), the resulting negative pressure and thus the response behaviour can also be changed here.

air pockets

Some types of slides (e.g. 8492-4 orig. PX200) have central cut-outs with a large radius on the underside (side facing the crankshaft). These are often erroneously referred to as cutaway. These pockets enable the carburettor to contribute air in a controlled manner to the mixture at medium slide stroke. If the engine rings in the partial load range at medium slide position, a change to a closed slide type (e.g. 8492-1 orig. Cosa200) can help.

b>bypass pocket

Some slider types (e.g. 8492-5 orig. T5) have a small pocket at the beginning of the slider at the left corner, seen in driving direction. This ensures a bypass of the auxiliary nozzle with little slide stroke. Here the transition area from idle system (mixture screw) to mist eliminator supply is increased, the mist eliminator starts to deliver mixture earlier with the same slide position. Ideal if thermally critical engines are to be operated at high speeds (highway) with little slider stroke (slipstream).

(US)
AI-translation