One more thing to try. Start it and get it to full throttle, then open the high needle until it is really rich and let it run that way for a minute or two. Now close the high needle until you get max rpm's and just back off a click. If the engine will run steady at this high speed setting then start on the low speed needle and get it to where it will idle good and transition well..Sometime when these engines have been sitting for a long time the oil congeals in the needle areas and act like a blockage that just doesn't clear out at normal settings but does with the needle open wide.
If this doesn't work I would be willing to look at the engine for you if you were willing to send it to me, I'm 50+ years in the hobby and have repaired engines for many folks over the last 30+ years. Lane