Mixture screw setting - new info

[Cougar]

I've always had good luck on any adjustable idle by turning the needle in until the motor begins to falter and noting the position, and then backing it out until it falters and noting that position too. I then turn the needle to be a split beteen the two positions. This may or may not be the exact same as the highest idling setting, but it does seem to run smoothly and seems to give the best coming off idle response.

[Gaz64]

Originally Posted by Cougar

I've always had good luck on any adjustable idle by turning the needle in until the motor begins to falter and noting the position, and then backing it out until it falters and noting that position too. I then turn the needle to be a split beteen the two positions. This may or may not be the exact same as the highest idling setting, but it does seem to run smoothly and seems to give the best coming off idle response.

Yes, you're correct in your procedure, but doesn't apply to the subject of this thread.

Zimmy has stated that there can be differences in the idle mixture screws between Italian and Spanish carbs.

The whole idle circuit could be a different calibration from factory, but the taper of the needle, its diameter and/or the port diameter affect the "correct" idle mixture adjustment point out from seated.

[Eljaro]

I did quite some trial and error with the idle jets and screw, and no matter what, the screw had to be 1 1/4 to 1 1/2 out for the setup to run right. I just discarded the 3/4 turn out setting for the idle as something impossible to achieve and am happy ever since.
That 3/4 setting was probably reached by someone about 40 years ago as the ideal. Well guys, if it is the carbs which are manufactured differently ( probably) or because of the global warming (less so), the setting is best at 1 1/4 out or even more.
Good to know that there is a modified mechanical dimension which may explain this and justify the new idle screw setting.