PROPERLY SELECTING AND INSTALLING CARBURETOR JETS

PROPERLY SELECTING AND INSTALLING CARBURETOR JETS

A guide explaining how to properly select jet sizes, and installation on PD24J carburetors.

Properly Selecting And Installing Carburetor Jets

Sizing at sea level:                                         [You must be registered and logged in to see this image.]
With UNI filter 120-125
With UNI filter and low restriction exhaust 130-135
With UNI filter, low restriction exhaust, A12 cam, performance coil & CDI and NGK Iridium spark plug 135-140

Test procedure:
1. Run engine at less than half throttle a minimum of 15 minutes to close electric choke
2. On a 300' or 100 meter stretch or greater, run the engine at wide open throttle
3. While still holding the gas pedal to the floor, cut the ignition
4. Remove the spark plug and inspect end for color
a. White - Increase jet size
b. Tan/Brown - Correct jet size
c. Black - Decrease jet size
5. Clean spark plug with brass wire brush and check the gap prior to next test run

Hints:
1. Change jet size by 2 or 2.5 for fine adjustment by 5 for coarse adjustment
2. Reduce jet size by 2 or 2.5 for every 1500 ft or 500 meters of elevation
3. Stock fuel delivery may not be sufficient above a 130 main jet and may require larger diameter fuel lines and less restrictive fuel filter
4. Once main jet is selected, the air/fuel mixture screw can be adjusted for optimum idle