Mechanical carburetors adjustment tips

Mechanical carburetor tuning tips is to know the mixture now is rich, lean or adequate.
The better way is to supply additional air flow in the mixture, look, discern and feel the rotation would gain or loose. The retarding vacuum nipple on Solex 34PICT3 is fixed at the position between throttle butterfly and intake valve, it convenient to give additional air as an experiment.
On the other hand, giving additional fuel often causes plug smoldering state and the firing sometimes becomes unstable with no relation with later adjustment, loosing sweetest points.
Overheating and plug smoldering make the carburetor adjustment difficult basically.
So, firing condition in every cylinder must be kept clean and adequately cool while the adjustment procedure.

WEBER mechanical side draft 40DCOM is different, looks one piece but the throttle butterflies are double, so the butterflies are set on every cylinder promptly.
On this type of carburetor also the key to the fine adjustment is nothing but the idle adjust screw setting. Because the idle setting affects middle and high rotations definitely.
After closed throttle butterfly setting so firmly as to even suction vacuum pressures being same value, the throttle is opened to rotate the motor using only with middle speed nozzle without idle spray, all the idle adjust screws are closed keeping the motor rotation over 2000rpm.
Then the only one idle adjust screw is opened gradually till it gains rotation a little, this very beginning position of the idle adjusting screw is marked.
This marking would be the key to success in the adjustment.
After closing finished cylinder,same procedures are repeated one by one as to the number of cylinders.
If the idle screws are set at the decided position, idling would be so stable as to pass the legal Exhaust Emission inspection though the values are very near to the limited ones,CO 4.5% and HC 1300ppm.
The best mixtures would be obtained if very very slightly opened from the marked position.