This saw has only about a couple of hours on it but is several years old. I used it about a year ago and it ran fine. I ran the gas out of it before storing it. Today it will not run a full speed, only 3/4 and then will cut out periodically. However, it does idle fine. Now I just noticed that if I run it at about 1/4 choke, it will run at full speed. The filters are obviously clean and I put a new plug in it as the old one was black, and removed the spark arrester which was clean. I tried to adjust the carb but to no avail. You can only turn the screws a half turn or so. Any ideas or is this just another carb I will have to rebuild because of ethenol? I have recently converted to non-ethenol fuel.