I have a fairly new evolution 40 cc that I like and has a good amount of power. However, I am having trouble tuning it. It idles good and high speed is good. When I slowly advance from idle to high it goes through a roughness in mid range and then jumps to high speed. My last flight I was going at a mid throttle for a few minutes and when I advanced the throttle quickly the engine quit. Luckily there was little damage. I was able to repeat the problem on the ground. I'm not too familiar with tuning gassers. Any suggestions?