This thing is driving me nuts. First it seems that the idle stop screw that has the vaccuum to it stopped working so I had to put in an actual screw that goes through the throttle linkage and stops against the manifold. That worked for a while but the damn thing now fluctuates from 1500rpm to 500rpm and still dies outright on occcasion. Goosing the throttle will sometimes knock it down but not always. As far as I know it's a non feedback carb. Can anyone help?

Did you check all your vacum lines for cracks and leaks. My hitachi has an internal vacum leak and i have to keep the idle up to like 1200 rpms to stay running.