Sorry, I didn't see the thread switch. I still have a hard time believing that I would need to drill a hole in the carb that the engine manufacturer matched to the engine. Now, if it was switched out for an after market carb....maybe.

I think people sometimes don't realize is that all of the mixture controls overlap to some degree and if things get totally out of whack, things won't seem to be working anymore the way the book says. And, in that case, you HAVE TO start over....

I mean, for example, take an engine perfectly tuned. I could set the idle set screw down so the engine idles faster and then then open the air bleed or low throttle mixture screw to slow the low end back-down to idle... what I end up with is a screwed up setting but at the same RPM idle I just had before; however, a screwed up setting that is unreliable.

Getting things out of whack...can happen on an air-bleed carb or a true air mixture screw setting....