Cause for hub failures?

I was at Elsinore yesteryday, and the guy parked next to me had a brand new YZ125 with only 3 hours on it. His rear hub failed at the sprocket carrier. I notice the (stock) sprocket had a radius on the inside to the mating surface of the hub. This is stupid. This would promote the sprocket pulling sideways under a load, away from the mating flanges and causing the failure. Im betting all the hub failures are with the stock sprockets. The seat on the hub isnt very wide at all, maybe 2 or 3mm from my glance. If you remove the edge of the sprocket, where in the heck is the seat? In my opinoin, its asking for a problem.

Both of my hub failures were with aftermarket sprockets. One touched against the insided of the hub, the other didn't. I think with the 426 that it just eats a hub when it gets hungry.


I noticed this past weekend when swapping sprockets that the allen head sprocket bolts are real weak. I snapped one in half with a little more torque than neccessary on the nut. If you are over tightening the nuts they (the bolts) will weaken & break. This may be one of the culprits to the exploding hub issue.

GA426 that wouldnt surprize me either, all of the bolts were sheared off except one. Ya gotta remember, this was a 125, not a 426. And I saw the bike before he took off, the chain wasnt too tight.

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