Main Jet Set Polini Dell'Orto SI

What is The Job of a Carburetor Jet?

A carburetor jet is a small hole in the carburetor through which fuel is drawn in and mixed with air. The jet's hole diameter determines the amount of fuel that flows through the carburetor, and thus the amount of fuel that is eventually burned. There are normally two types of jet in the carburetor of motorcycles, scooters or mopeds:

• The main jet
• The pilot jet, also called slow jet

Choosing the right carburetor jet

Choosing the right carburetor jet is critical to ensuring that the engine can run optimally.

• If the jet is too small, the engine will run too lean and may overheat.
• If the jet is too large, the engine will run too rich, resulting in excessive fuel consumption and lower performance.

The colour of the spark plug can be "read" to check the settings:

• White = too lean.
• Black = too rich.
• Brown = perfect.

It is important to choose the right jet for the type of carburetor you are using, as each carburetor has its own jet type.

And here's our detailed spark plug tutorial.