2 Stroke Tuning Software How To Change Your

As the throttle is opened, the needle allows fuel to pass by the taper and between the straight portion of the needle and jet wall.

Once you understand the basic functionality of one 2-stroke carburetor, you can apply that understanding to ANY carburetor.

Although some may have different configurations or features, they all do the same thing mix fuel and air.

2 Stroke Tuning Software How To Change Your

Knowing how to change your jets and needles is one thing, but it wont do you any good if you dont understand how the changes will affect your dirt bike.

Parts of the Carburetor and What They Do Carburetor Body Body The carburetor body houses all the moving parts and jets, and mixes the air and fuel on its way to the cylinder.

The bowl also houses the float assembly.

Stroke Carb Body And Bowl Internal Carburetor Components Float Assembly The float assembly sits inside the bowl to regulate the fuel level in the carburetor bowl.

The floats are made of hollow plastic or metal connected to the carburetor body by a hinge.

Plastic Float assembly Float Valve The float valve regulates the flow of fuel from the fuel tank to the carburetor bowl.

Stroke Carburetor Float Valve Seat AirFuel Flow Pilot Air Screw Controls idle speed by regulating the amount of air passing through the pilot jet passage.

This is where you will spend a lot of time during 2-stroke carb tuning.

Pilot Air Screw Throttle Valve The throttle valve is directly connected to the throttle cable and regulates the flow of air through the carburetor.

You will almost always find a slide style throttle valve on 2-stroke carburetors.

Throttle Valve Parts Valve Assembly Closed Half Open Open 14 Open With Jet Closed Without Needle 2-Stroke Carburetor Jetting Structure Slow Jet 2-Stroke Carb Adjustment Slow Jet The slow jet works with the pilot air screw.

This system controls the air-fuel ratio from closed throttle to throttle.

The slow jet draws fuel from the bowl and mixes it with air from the pilot air jet passage.

The atomized airfuel mixture then passes into the throat of the carburetor.

Turning the pilot air screw in will richen the airfuel mixture while turning the screw out will lean out the mix.

The slow jet is interchangeable with jets that will provide a leaner or richer air-fuel mixture.

Replacing the existing slow jet with a higher numbered jet will make the mixture richer, while a lower-numbered jet will make the mixture leaner.

Jet Needle The jet needle is connected to the throttle valve and controls the mixture from approximately throttle.

The needle seats into the needle jet and regulates the air-fuel mixture from the jet to the carb throat.

During your 2-stroke carb adjustment, pay close attention to the needle.

The jet needle regulates fuel by its taper, diameter, and clip position.

In the closed throttle position, the tapered needle shuts off flow from the needle jet.