Went to a track on Saturday for a bit of practice, did around 5 laps and heard a bad noise coming out of a slow corner. Stopped to find the rear sprocket completely broken away from the wheel! Never been one for aftermarket wheels before but now I have no choice. Anyone else seen this happen? I'm not suggesting its a fault, more likely some bolts came loose as I've been chasing that fairly regularly since the bike was new. The stock honda sprocket bolts seem to stretch a lot.. BUT even so the hub seems very week that a loose or broken bolt could destroy it like this? Bike has done 20 hrs. Looking closely there's a darker area to the casting as shown with the arrows, which suggest to me that it was cracking some time before it broke, or there were some differences in the casting mix? I don't know, check those sprocket bolts and be careful..