Air corrector jet -DELLORTO (type: 5827) SI-

The air nozzle (exactly: main air correction nozzle) of the SI carburettor has a big influence on the amount of air provided to the premix. The available pallet ranges from 120-190. A 120 air nozzle has a bore of only 1.2mm, thus providing very little air and is greasing accordingly. A 190' air nozzle provides a lot of air and is therefore very lean.

Function nozzle block SI

In the nozzle block area of the SI carburettor (depending on the filling level in the float chamber) there is always a defined fuel level available. I.e. below the atomisation tube (which opens into the intake area of the carburettor) there is a petrol column. For this reason we also advise against the so-called float chamber spacers. These increase the filling level in the carburetor, but also ensure a higher level in the nozzle block area, which means that the premix can no longer work properly and possibly even fuel from the atomizer runs directly into the engine (sink). The actual problem is also not a too small volume of the Schhwimmerkammer but an e tuning over the air nozzle (see below).

From the very bottom by means of the main nozzle the following petrol quantity is defined. In the middle is half in the gasoline, half in the air, the so-called mixing tube (e.g. BE3). If the air nozzle is too large (e.g. 190), no sufficient negative pressure can be created and the fuel supply under full load is dangerously low or collapses completely (often confused with emptying the float chamber). In this case, raising the main nozzle will only help to a limited extent if at all.

This phenomenon often also occurs with modified series air filters, where the hole drilled subsequently above the air nozzle is too large for the engine's requirements (e.g. 8mm).

Similar happens when using air funnels from Polini or Pinasco, which are mounted instead of the air filter. In order to compensate for these modifications, not only the main nozzle must normally be considerably larger, but also a smaller air nozzle must be used (e.g. 140 instead of 160).

TIP

Series motors with series filters can usually always cope with a 160 air nozzle. Tame tuning variants such as a Pinasco 213 can also be operated with the lean 190/BE4 combination (original PX200 10HP variant) (but never with a modified air filter). A high power engine tuning may also require an air nozzle with only 140 or less to avoid slimming under full load.

(US)

(machine-translated)