My craftsman 3.7 (poulan 3800) will start and idle fine but has no power to rev. Very weird because I just bucked and noodled a 25' long, 24" diameter oak log with it a couple weeks ago, cleaned it with air and put it on the shelf. Got it out yesterday and it won't rev. The only time it started to rev is when the H screw was almost all the way in. Just wondering if the issue sounds familiar to anyone and could suggest something