[Healeys] HD8 adjustment

[warthodson at aol.com]

When adjusting HD type carbs, I generally prefer to back off the fast idle
screw so that the throttle is fully closed (after disconnecting any
interconnecting linkage) & attempt to set the idle speed with the idle screws.
I have no trouble doing this with HD4 & HD6 carbs. Including tricarb cars with
both HD4's & HD6's. Yes, I know those are not the original tricarbs. My
problem & question concerns the HD8's which seem to defy being adjusted this
way. I never seem to be able to open the idle screw far enough to increase the
idle speed to an acceptable level. In many of these cases the HD8's have been
recently fully restored professionally & the cars are in very good condition.
Am I correct in believing that this is a common problem?  If yes, what are the
theories that explain why HD8's behave this way? Yes, I know there are two (or
more) schools of thought on how to adjust carbs.
Thanks,
Gary