My 1200 just recently started making a strange whining noise when riding at speed. If I slow down to like 10mph it stops and doesn't start up again when I speed up, but after a few minutes of riding it just starts all of a sudden. It's fairly loud and seems to be coming from somewhere in the motor. As I slow you can really hear it as the motor quiets down, but then it just stops as I get really slow. What could be causing this?