on the outboard side of the carbs, the idle mixture screws are the ones with springs on the shaft (to preload them so they do not get loose)
In is lean.
Out is rich.
(first warm up the engine... get it to idle)
1. Disconnect Linkage
2. Measure flow of each barrel.
3. They should be close/exact. (especially on the same carb!)
4. when they are all exact flow, you can start messing with idle mixture
5. start with one carb and one barrel. Slowly turn the mixture screw INward about an 1/8 turn at a time. The idle should go up (leaner) and eventually that cylinder will die (too lean)
6. Back out the adjuster in the same way about an 1/8 turn at a time, until you are just past that high idle spot. (just a tad rich of the high idle)
7. Do this with the other 3 barrels.
8. Then you can adjust the idle stops to make both carbs flow the same
At the end of this, you will have a nice idle mixture, and all your adjuster screws SHOULD be around the same # of turns out, and should all flow the same.
If there is a flow differential between the 2 barrels on one carb, you *CAN* adjust this with the air bleed screws.
I have stressed this, but i IMPLORE you to buy the CB performance book on Weber Carbs. Mine went missing
but it teaches you everything about IDF carbs.
once you understand what each part does, you ca understand how the changes work
claude does a great job of explaining