Dellorto A02 Needle

The Dellorto carburetor needle

The characteristics of the carburetor needle are:

    - The diameter A of the cylindrical part

    - The length C of the tapered (conical) part

    - The diameter B of the tip

The needle must be selected, taking into account the elements listed above, so that all work phases are optimally controlled. The cylindrical part of the needle determines the mixing ratio up to about 1/4 throttle opening. In this working phase of the carburetor, a reduction in diameter (A) means an enrichment of the mixture, while an increase means a lean mixture. The conical part of the needle (C) influences the working phase of the carburetor between 1/4 and 3/4 of the throttle valve opening. An increase in the diameter (B) of the needle with a constant length (C) and constant diameter (A) leads to a leaner mixture, a decrease in the diameter (B) leads to an enrichment of the mixture in this phase. If the diameter of the needle tip and the cylindrical part remain the same, a change in length of the conical part (C) causes the mixture to accumulate earlier. By changing the needle position (1 - 4th notch), a change in the mixture can be achieved in the phase determined by the conical part of the needle (if the needle is hung higher, the mixture will accumulate earlier).

If major changes to the mixture composition are required, the needle must be replaced according to the elements and properties described above.

As a rule, the gas valve spring pushes the needle in the direction of the atomizer. The fixed position of the needle and the atomizer ensures a constant fuel supply and reduces wear and tear caused by vibrations that may occur.