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Ford Carter YF Idle Speed Adjustment
Normally the idle speed and mixture adjustments are the final setting make on the carburetor. On a Carter YF carburetor that has a dashpot or electric solenoid, the idle mixture setting is done prior to setting the dashpot, or solenoid.
Idle speed and mixture adjustments are made to ensure a smooth operating engine. More importantly, however, the air-fuel ratio is established which also provides a cleaner burning mixture.
Idle Settings with the engine off
On Carter YF model carburetors, establish an initial idle mixture screw setting by turning the screw inward until it is lightly seated, then turn it outward 1 to 1-1/2 turns. Do not turn the screw tightly against the screw seat, as this may damage the end of the screw. If you do damage the screw, then it should be replaced.
Back off the idle speed adjusting screw until the throttle plate seats in the throttle bore.
Be sure the dashpot or solenoid throttle positioner, if equipped, is not interfering with the throttle lever. It may be necessary to loosen the dashpot to allow the throttle plate to seat in the throttle bore, or if a positioner is involved, disconnect the ignition switch lead at the connector. This will inactivate the unit, causing the plunger to retract.
Turn the idle speed adjusting screw inward until it just makes contact with the screw stop on the throttle shaft and lever assembly. Then turn the screw inward 1-1/2 turns to establish a preliminary idle speed adjustment.
Idle Settings with Engine Operating
For automatic transmission type of cars, set the parking brake and block the wheels of your car. You will be adjusting the mixture while the car is in drive. The engine must be at operating temperature before idle adjustments can be made. Run the engine for 20 minutes at 1500 rpm. Use the high step of the fast idle cam on the carburetor to establish the 1500 rpm.
Check the initial ignition timing and the distributor advance and retard. Use a tachometer when checking the initial ignition timing and idle fuel mixture and speed settings. On manual transmissions adjust the idle setting with the transmission in neutral. On automatic transmissions the settings are done with the transmission in drive.
Be sure the choke plate is in the full open position.
Adjust the engine curb idle rpm to specifications. Make the adjustments with the air cleaner installed. If you can't get to the adjustments, then remove the air cleaner, make the adjustments, then re install the air cleaner and take your readings again.
Turn the idle mixture adjusting screw inward to obtain the smoothest idle possible.
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