Idle trimming screw

[randerson@postman.cfaluminum.com (Rick Anderson)]

I have a 76 TR6 which has ZS carbs.   A mechanic just rebuilt the carbs
before I bought the car and has it running too rich.   I have colortune, jet
adjustment wrench and syncronizer and want to tune the carbs myself.   The
Haynes book gives fairly good directions on that procedure but I'm curious
as to what the idle trimming screw on the side of the carb body does, and
what are their approx. settings.    Any help would be greatly appreciated.

Ric