Water pump shaft and selector part # 1SL-18140-01-00. I have heard that Yamaha is aware of this issue. I don't know anyone that has had this fail. It is a bearing that fails and is replaced with a bushing. There was some discussion on another forum so I was curious. My bike has been perfect, but it only has 16 hours on it. The 2 reported failures on the other forum occurred around 35 hours.