Hello all. I'm new to this forum, as well as small engines,so I hope I can get some help here. I have a 55 rancher (has been nothing but a lemon but I'm persistent). My problem now--the bar continuously slips allowing the chain to come loose constantly. The small black threaded guide that engages the bar for tightenting (or loosening) will not stay in its housing on the saw body. What holds it in place? have I sheared a small retaining pin? I'm about to shoot the saw!