Problematic [:'(] I don't like the sound of that. Nothing worse then seeing a guy spending a lot of time tinkering on an engine thats not running right instead of flying. I do have a large mixed collection of YS .60 FS/FR engines with 3 of them NIB. Perhaps I will just stick with using those and see if anyone else would like to buy the two ARs I have. One them is also NIB. Dave, I thank you for all your time and information.