I know it's hard for everyone to describe a sound and even harder to help diagnose, but here goes. The best description I can give is a chirp/squeal. I can't tell if it's coming from behind or under. When my wife was riding with me, she couldn't tell where at either. I know it ONLY does it while accelerating. If I pull the clutch in and rev, it won't do it. When I let off the throttle it will stop (if it was doing it). I just started hearing it a few weeks ago. It runs fine, I just hear the noise. I have about 9500 miles on it, 2013 XC with Stage 1 kit, purchased used a few months ago. I initially thought it was something with the Exhaust because if when I hear it. But now I think it might be belt, but not sure since I don't know what that sounds like. Any thoughts?