So I just went for a night ride, 21 km run. About half way, I hear this horrible grinding noise. I stop, clutch, idle, still there. I realized it was from inside the engine, and not the bike. I waited for the engine to cool, and then I removed the right side panel. When I looked at the gears, it seemed fine, until I noticed that the long slotted flat head screw holding the small sprocket on, was about to come off! The grinding was the screw itself, grinding into the panel! There is a small ground disc on my cover now, where the screw was grinding. So, I used an allen key to jam the gears, and tightened the screw as much as I possibly could. I replaced the cover, and started her up. It was fixed, got me all the way home again. Whew, That was a catastrophy narrowly averted! If I've learned anything about these engines, is you need to learn to listen to it. The engine will tell you when something is wrong, and when you detect a difference in it's performance, you should stop immediatly and inspect, don't run it to see if it will fix itself. lol, You may avoid a breakdown with a fast reaction time. So, has anyone ever had this happen? Why would it have come loose in the first place? Will it likely happen again? Thanks guys, later.