Topic: Old-School Carb Tuning Theory Opinions?

[736cc]

When synching 4 carbs, the air screws are simply set to factory specs (ie:1 1/4 turn out). But, if carb vacuum gauges are set-up, shouldn't the air screw settings be optimized and be set based on the maximum vacuum reading? And then get all 4 air screw vac readings roughly the same? If I remember correctly about old-school carb-tuning on cars (single carb) a tuner would bottom-out air screws then turn them out until rpm's dropped (just by listening), then turn air screw back in slightly. Or was it vice-versa? (back air screws out several turns, then turn them in until rpm's dropped then turn out slightly?)
If this additional air screw adjustment is added to routine carb vacuum synching, is this done first or last?
And I'm doing this on K0 carbs, which I've done many times but always looking to improve.

[05c50]

I've often considered that question. I was a auto mechanic back in the day of adjustments. We (me and the guys I worked with) would always adjust the mixture screws until the highest idle speed was reached and then turn the screws in a quarter of a turn. I do this same thing on my bikes.

........Paul

[Bodi]

The vacuum balance is for the throttle slides. The airscrews adjust closed-throttle mixture, and will not affect the vacuum balance. You should adjust the airscrews for best idle (and then I richen them up a bit for better off-idle pickup for carbs without accelerator pumps). Whether to do this before or after vacuum sync... I would do it after when all 4 carbs should be at the same throttle setting. If one cylinder is pulling harder than the others that could confuse the airscrew setting procedure.