Thanks so much Bill - this is awesome. Looking through those pages I see that there are a number of washers missing (but they may be in the kit.) The choke spring is also missing, As you suggest, that is probably the source of the problem. I was suspicious because the idle adjustment screw (not the mixture screw) lands on a strange part of the fast idle/choke linkage. One would think it would land on the large flat area even though that is mainly for stopping on the carb body. But where the screw lands now looks freshly burred, so something weird has happened recently. Hopefully, I can find some carb parts tomorrow at the big swap meet in Abbotsford.
This documentation is much better that the kit instructions. Once again, I owe you big time!