I know it'been a few months, but any resoloution?
Chasing this issue myself.
Cranked it in the dark and seeing spark around a couple plugs. (NGK FR5's, also different carb, Edelbrock Thunder 800cfm)
Hello. No I wasn't able to get rid of it. Will have to try again in the spring as the ol' dog is parked for the winter now. Frustrating as hell though, but if one thing has been gained is my knowledge of that carb and knowing my way around it. I haven't fired it up in the dark and looked for spark, so I guess that's an idea. Didn't think I would need to with new plugs, wires, cap, coil, etc, etc, etc, but ya never know. I will also pay attention to those back butterflies also. I'm will to try anything as I'm really running outta ideas.