All good suggestions ..already have 4-40 linkages and ball joints and have taken throttle loose while running and held the throttle closed to make sure it is closed fully..I replaced the butterfly cause the old one did have some very small dings where it had over time rubbed against the throtle bore..looking through the bore the only light is the small notch at the bottom of butterfly which is factory.

The carb didn't have a spring on the shaft when I bought it but the slack was taken up with a nylon washer so the butterfly would not move back and forth. I have replaced all gaskets including the carb base gasket. The engine starts great and runs good at high RPMs

The crankcase halves gasket does appear to be wet and might be leaking but not sure if this would cause idle problems. I even sprayed WD40 on the throttle shaft and other gasket areas while running to see if there was a vacuum leak and didn't detect any change in RPMs.I'm out of things to do..anyone else have any more suggestions/

Hey Ralph do you have any suggestions?