Saturday my buddy and I went riding. The first thing I check is the back sprocket, because I have lost a bolt before. Well my friend took my bike out on the track. I took his cr250. While he was going around the back sprocket fell off. Luckily he was riding because he is a better rider and if it was me, I probably would have got f'd up. Is this a problem that everyone else is having? AND the holes in the hub are starting to Oval, can this be a warranty issue? On another note, I did do the BK mod, and definatley liked the snap coming out of the corners. Also, after riding the 2-smoke, I may be going back to the 2 smoke. Much nicer ride for me, especially at 5'5".