I just got an EVO .61 that was stuck in a tree for 4 months. After cleaning it up (getting rid of some of the rust), it started up and has run fine since. I have had trouble with some EVo on various trainers that my students have. Mostly mid-range transition. On one of the trainers, I just had him remove the Evo and use one of my old OS 40 FP - have not had any trouble withthat engine at all. Being an old-timer, I've owned many brands. The only one that I ended up junking was a Tower .40. IT never ran right. I still love OS engines, but I am not afraid to use other ones, both 2 Stroke and 4 Stroke.