Ok, I know it isn't a chainsaw, but I thought some of the helpful folks at ArboristSite may have run into a few of these things. My problem is poor midrange and nonexistant idle. Once you get it to full throttle, It runs OK, but it doesn't seem to run like it should. No matter what I do with the "L D" screw it runs the same. It idles for about three seconds, idles up a bit, then dies. If I understand this carb, turning the screw clockwise richens and counterclockwise leans idle. There are no other adjustments on this carb. I have inspected the piston and bore and it is clean as a whistle, no scoring. I replaced the fuel line and filter with the new green one. I have had the carburetor apart multiple times and it looks clean. I have pressure and vacuum tested it and it passes. New air filter. New tank vent. No matter what I do to this thing, it runs the same. I have used it personally for about 6 or seven years. It has been running this way for about 3 years. I use it regularly, year round. I don't use it for long periods of time however. I suspect it has under 100 hrs of use. At this point, I am looking to replace the carb with something adjustable. No matter what i do with this thing, the plug reads slightly lean, at all RPMs Am I missing something here? This thing is making me doubt my mechanical ability.