Mixture Control Solenoid Adjustment Procedure

1. Remove air horn, mixture control solenoid plunger, air horn gasket and plastic filler block, using normal service procedures.

2. Remove throttle side metering rod. Install mixture control solenoid gaging Tool JD-33815-1, BT-8253-A, or equivalent, over the throttle side metering jet rod guide, and temporarily reinstall the solenoid plunger into the solenoid body.

Installing Mixture Control Solenoid Gauging Tool:

Adjusting Lean Mixture Solenoid Screw:

3. Holding the solenoid plunger in the DOWN position, use Tool JD-28696-10, BT-7928, or equivalent, to turn lean mixture (solenoid) screw counterclockwise until the plunger breaks contact with the gaging tool. The adjustment is correct when the solenoid plunger is contacting BOTH the SOLENOID STOP and the GAGING TOOL. If the total difference in adjustment required less than 3/4 turn of the lean mixture (solenoid) screw, the original setting was within the manufacture's specifications.

4. Remove solenoid plunger and gaging tool, reinstall metering rod and plastic filler block.

5. Invert air horn and remove rich mixture stop screw and rich authority adjusting spring from bottom side of air horn, using Tool JD-28696-4, BT-7967A or equivalent.

Removing Rich Mixture Stop Screw:

Removing Lean Mixture & Rich Mixture Stop Screws:

6. Remove lean mixture screw plug and rich mixture stop screw plug from air horn using a suitably sized punch.

7. Reinstall rich mixture stop screw and rich authority adjusting spring in air horn and bottom lightly, then back screw out 1/4 turn.

8. Reinstall air horn gasket, mixture control solenoid plunger and air horn to carburetor.

Adjusting Rich Mixture Stop Screw:

9. Insert external float gauge in vent hole and with TOOL JD-9789-130, BT-7220 or equivalent , adjust rich mixture stop screw to obtain 4/32" total plunger travel.

Installing Lean & Rich Mixture Stop Screw Plugs:

10. With solenoid plunger travel correctly set, install plugs (supplied in service kits) in the air horn, as follows:

a. Install plug, hollow end down, into the access hole to lean mixture solenoid screw and use suitably size punch to drive plug into the air horn until the top of the plug is even with the lower edge of the hole chamfer. Plug must be installed to retain the screw setting and to prevent fuel vapor loss.
b. Install plug, with hollow end down, over the rich mixture stop screw access hole, and drive plug into place so that the top of the plug is 1/16" below the surface of the air horn casting. Plug must be installed to retain screw setting.