Mixture Screw Packing Installation

The mixture packing consists of a spring, washer, and o-ring. These are found under the carburetor mixture screw in all Harley/Keihin CV and Butterfly carburetors. The mixture packing is designed to apply tension to the mixture screw and create a seal to prevent leakage past the screw. When installing a new EZ-Just mixture screw or reinstalling the existing mixture screw, it is important to install the packing in the correct order.

Below is the order of each part.


It is important to have the washer placed between the spring and o-ring. This prevents damage to the o-ring from the sharp edge of the spring.

See our Mixture Tuning Guide for instructions on installing the mixture screw or EZ-Just.


Replacement Mixture Packing Kit


Note: Do not substitute the o-ring with a standard rubber o-ring. Fuel additives found in pump gas will deteriorate a rubber o-ring and melt into tiny passages. Only use o-rings made from Viton or similar resistant compounds.