Jetting - Main Jet, Pilot Jet, Needle Jet - What's the difference?

 

The main jet, pilot jet, jet needle, and carburetor tuning are important components of the carburetor system in a small 2-stroke engine. These components work together to provide the right fuel-to-air ratio for the engine to run smoothly and efficiently. Here is a guide to understanding these components and how they work:

Main Jet: The main jet is a small tube that controls the flow of fuel into the carburetor. It is located in the carburetor bowl and is responsible for providing the majority of the fuel needed for the engine to run at high speeds. The size of the main jet determines how much fuel is flowing into the carburetor, and the fuel-to-air ratio can be adjusted by changing the size of the main jet.

Pilot Jet: The pilot jet is a small tube that controls the flow of fuel into the carburetor at low speeds. It is located in the carburetor throat and is responsible for providing the fuel needed for the engine to idle and run at low speeds. The size of the pilot jet determines how much fuel is flowing into the carburetor at low speeds, and the fuel-to-air ratio can be adjusted by changing the size of the pilot jet.

Jet Needle: The jet needle is a small rod that controls the flow of fuel into the carburetor at mid-range speeds. It is located in the carburetor throat and is responsible for providing the fuel needed for the engine to run at mid-range speeds. The shape and position of the jet needle determine how much fuel is flowing into the carburetor at mid-range speeds, and the fuel-to-air ratio can be adjusted by changing the shape and position of the jet needle.

Carburetor Tuning: Carburetor tuning is the process of adjusting the main jet, pilot jet, jet needle, and other carburetor components to provide the optimal fuel-to-air ratio for the engine to run smoothly and efficiently. Carburetor tuning can be done using a variety of tools, such as a carburetor syncing tool, a fuel pressure gauge, and a tachometer.

Here is a comparison of main jet sizes and types: