Jet -DELLORTO (type: 11600)- 4mm (38)

The main jet is considerably involved in the mixture preparation of the carburetor.
If it is too small, the engine dies off under full load and/or runs so leanly that the piston including cylinder overheats and a cylinder damage would be the consequence.
If it is too large, the mixture is too rich, the engine runs very unevenly and can only deliver a fraction of its possible power.

To determine the correct main jet, it is first of all selected from the belly so large that the target is an engine that stutters heavily under full load. Of course it needs some experience, but a nozzle is also quickly changed.

Once you have found such a nozzle you mount a smaller nozzle until the engine does not stutter under full load any more.

This way you have already an ideal basic lubrication which ensures that the engine does not get too little fuel under full load, which it also needs to cool the piston and cylinder. The Dell'Orto carburettors in conventional slide valve design, where the main jet is positioned directly in the float chamber (no SI carburettors), use as:

secondary jet 4mm / 5mm

main jet 5mm / 6mm

jets.

The 4mm nozzle type is used exclusively as a secondary nozzle, although it would mechanically fit into other carburetor types of Japanese origin as a main nozzle.

Used in the following carburetor types as a secondary nozzle:
PHBN, PHVA

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