Well I have a 2013 kx250f and there's a serious problem I encountered last night while riding. Yeah I don't get it! Axle nut was tight, it was ligned up perfect and the chain wasn't loose at all. The left adjuster that holds the axle block back is locked up and the nut won't move?? I didn't tighten them that much, just snug. The chain guide is yanked back too like it bent the bolts on it!