I have posted this here along time ago. One of the MX mags said Yamaha has had numorous hubs fail. Mine blew up on both myh 400 and my 426 (both I have sold and because of the clutch problem on the 426 I may never own a Yamaha again). What happens is the sprocket bolts back out or break or both. One way to protect yourself is to buy high tensile strenth sproket bolts (Moose carries them) and tighten them tighter and red lock tite them. You still must check them but at least it will not self distruct in one ride.