weber tuning, questions Options

[r_towle]

ok,
So I have one rich and one perfect plug on one side...

I will use the idle mixture screw to adjust this condition...

What is the air bypass screw for, where do you guys set it, and how does it change the way the carb tunes??

I was having some sooty exhaust, so I checked the floats..perfect..if not just a tad lean...11mm which is ok with me...

Rich

[TimT]

Ive been tuning Webers 3bbl weber for over 25 years, Ive found there is alot of info floating around that needlessly complicates what is really a pretty simple procedure.

the way I do it:

disconnect throttle linkage

raise idle to about 15-1800 rpm

adjust airbleeds (close them, check airflow, adjust to highest flowing stack)

reduce idle to desired rpm via idle adjustment screws (check bank to bank flow with unisyn)

adjust idle mixture screws (one cylinder at a time), turn in until cylinder stumbles, then turn back out till it fires again.

go over the idle mixture screws a few times fine tuning

install throttle linkage such that there is no preload

turnoff engine, check that butterflies open when go pedal is fully depressed, adjust linkage as needed

Once you set the air bleed screws you should never have to touch them again

thats the way I do it, its a distillation of all the other methods Im sure, but its simple to me, and it works