What follows is a
rough guide, based on experience on my part and the procedure as explained in the workshop manual:
The mixture setting should not be adjusted until the ignition system is checked and confirmed to be set correctly. Once this is done, proceed as follows:
Make
SURE the gear selector is in neutral, then start the engine and allow it to reach normal operating temperature. Turn the idle speed (tick-over speed) screw in a little, to raise the tick over.
The mixture screw is screwed IN to weaken and OUT to richen it. Screw
in the mixture screw g-e-n-t-l-y in until the engine runs unevenly or sounds "lumpy", then unscrew it 2 to 2 1/2 turns. If the engine stalls, re-start it.
Adjust the tick-over speed to the correct setting, which is best set by a rev counter, to ensure the clutch is disengaged at idle.
Now either depress the brake pedal or operate the low hold switch: this weakens the mixture, as the valve is opened to the primary unit and this should cause the revs to
rise slightly. If the car stalls when the brakes are applied, the mixture is too weak and the mixture screw should be unscrewed a little more. If it is necessary, do this in quarter (90 deg) turns at a time. The mixture must be adjusted to avoid the car stalling when the brakes are applied.
Take the car for a drive, and include some sustained long braking, down a long gentle hill for example, to confirm the engine doesn't cut out when the brakes are held on for a period of time. Adjust the mixture screw again if necessary and then confirm the gear selector moved smoothly between forwards and reverse without crunching. Adjust the tick-over if it doesn't.
Alternatively, if you have a classic-friendly garage that has an exhaust analyser, ask them to hook up the car and set the mixture to 3.5-4.5% CO at idle.
That
should do it.......
