Zama Rotary Carb K-66B
That diagram carb shows the Main Mixture screw BEHIND a retainer ball. The ball is part # 33 and the main mixture screw is part # 34. But, your carb is different. That diagram is for reference only. Do you see what I mean? Both of these parts go in the diagram carb in front of the plug according to the diagram. The jet plug and the O ring for it are listed as a kit at the beginning of the parts list for your carb with the rebuild kit, gasket and diaphragm kit etc. As the EPA regs progressed, we have been able to adjust carbs less and less. Let me know if you get the thing to operate correctly. I have to study the diagram further to see if there is anymore you can do. If the carb sucks air out of that plug hole on the K-66B...do you see anything else at all in there?