I have a sport with about 8 hours on it and I've noticed a rattling noise that sounds like it comes from the center directly under or behind the seats when I'm going in the 28-30MPH range. It doesn't do it every time, and it doesn't do it long. I'm thinking it might be related to the CVT but really can't tell for sure. It sounds like light weight metals banging together, maybe like a screw driver tapping a drive line somewhat rapidly. Anyone else ever hear something similar?