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

[hmeeder]

Rich;



I was going through all of this just a week back. According to the Redline Weber site the Air by-pass screws are not used to intially tune the carb (what the hell are they there for then?)

However an article on the Aircooled.net site did describe how to use the Air-bypass when sychronizing your carbs. It's more for the fine tuning of the individual barrels. If all 4 cylinders have equal compression and volume, then you most likely not need to adjust the Air-Bypass. Your issue sounds more like either lean idle adjustment or possibly a clogged idle jet. Float setting sounds correct.

Some Articles I found helpful:

How to Sync Dual Carbs

Redline Lean Idle Procedures

Jetting Theory

IDF Set Up

IDF tuning

Weber Tuning for Porsches

A couple of quotes:
"Loosen the 8mm wrench size nuts on the “air bleed” screws, turn in the air screws until it seats then tighten the nut."
"Most Critical! Be sure for initial carburetor set up all air by-pass screws should be in closed position. These are not commonly used in standard carburetor adjustment."