So I took off my head and cylinder this afternoon for an unrelated reason (winter boredom), and I noticed that my top piston ring can spin freely around the piston. The little pin that ordinarily keeps the ring in place is missing! I haven't noticed any problems up until now, and the sides of my cylinder aren't scratched up. I wasn't particularly violent when I took the cylinder off the piston, so I don't think that I dislodged it in the process of opening the engine. So my questions are, is there any chance that my engine has been running this far (~250 miles) without a pin to retain its top piston ring? Do you guys think I can just put everything back the way it was and be okay? I've looked around, and I can't find any vendor that sells piston ring retaining pins... What should I do?