IDLE SPEED AND FUEL MIXTURE

  1. Start the engine and allow it to run until it reaches operating temperature.

  2. Connect a tachometer to the engine.

  3. Disconnect the throttle solenoid lead from the wiring harness.

  4. Set the lower specified idle rpm, using the curb idle adjusting screw. It may be necessary to turn the adjusting nut on the throttle solenoid as well as the idle adjusting screw if the solenoid plunger interferes with the lever.

  5. Connect the throttle solenoid lead. Manually move the throttle lever slightly to allow the solenoid plunger to extend. Set the higher specified idle rpm by turning the solenoid adjuster.

    Screenshot 2025-06-18 at 12.32.59 PM.png

  6. Turn the idle mixture screw in or out to obtain the smoothest idle possible within the travel of the limiter cap.

CHOKE PLATE PULL-DOWN

Screenshot 2025-06-18 at 12.41.55 PM.png

  1. Remove the air cleaner assembly.
  2. Remove the thermostatic spring and water housing.
  3. Depress the vacuum piston until the vacuum inner bleed slot is exposed. Insert a length of wire 0.0040” thick into this slot. Raise the piston to trap the wire. With the piston and wire held in this position, close the choke plate until its movement is stopped. Partically open the throttle for the fast idle tab to clear the cam.

Check the clearance between the bottom of the choke plate and the carburetor body. This can be measured with a suitable drill or gauge rod. If not to specification, bend the extension of the choke thermostat lever (the part that rests against the vacuum lever) to adjust the clearance.

DE-CHOKE ADJUSTMENT

Screenshot 2025-06-18 at 12.43.48 PM.png

Open the throttle and holt it against the stop. check the clearance between the bottom of the choke plate and the carburetor body. If not within specifications, bend the projection on the fast idle cam. A drill or gauge rod can be used to measure the clearance.

ACCELERATOR PUMP STROKE

  1. Unscrew the throttle stop screw a few turns until the throttle plate is fully closed.
  2. Depress the accelerator pump diaphragm plunger and check the clearance between the operating lever and the plunger with a suitable drill or gauge rod. If not within specifications, bend the gooseneck of the pump push rod to adjust the stroke. Close the gooseneck to lengthen the stroke or expand it to shorten the stroke.
  3. Reset the throttle stop screw to its original position.
  4. Replace the air cleaner assembly.

FAST IDLE ADJUSTMENT

Make certain the curb idle speed and mixture are adjusted to specifications before attempting to set the fast idle speed.

  1. With the engine operating temperature normalized (hot), air cleaner removed and tachometer attached, manually rotate the fast idle cam until the fast idle adjusting screw rests on the specified step of the cam.