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2013 Broken rear hub

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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..

 

hub1.jpg

 

hub2.jpg

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My 09 crf450 seems to have some pretty crappy cast aluminum parts. Some of them have kind of snapped off with not much force applied to them. Idk if it's related or not but thats all I have to say.

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so what was left to unbolt ?

 

I see  some good mounting holes left were the bolts in there sitll ?

 

not sure if the stock bolts are streatching ? they should not have any stretching type loads other than the initial tourque then they are subject to   shear loads  unlike a cylinder head  ETC

Edited by Zimman

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Are your spokes bent?  It looks like one of the ones on the left side in the first picture is bent.

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there was just one bolt still in place on the sprocket with a bit of hub attached to it. all the others were gone, the wheel was as you see it, the sprocket completely detached. during the smash up process something must have caught in the wheel and bent that spoke, probably the sprocket

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Well I see this locally all the time on every kind of MX bike.

Usually there has been a sprocket change recently and the bolts were over tightened. Then the bolts crack and fall out (the ones where the hub holes are still intact) and the others are in the sprocket ripping the two apart.

The discoloring is common for heat treated cast parts.

If the bolts come loose, the bolt head will hit all kinds of stuff and scar up the swing arm, chain guide and all pretty bad. When they break from over tightening, they just fall out when they are broken in two.

I'm not saying you are at fault, or this is your case for sure, but it is very common and easy to do.

Jason

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I have exploded a rear hub myself and its not a good feeling for sure. A couple of tips:

Use red lock-tight on the threads and beveled area where the bolts contact the sprocket. I've never had any come loose after using this method.

Be sure that you aren't running your chain too tight and putting added pressure on your hub.

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Always check sproket bolts every ride. If they get loose it will shear the hub. 2choices. Get a old hub and use a spacer.... Or get a new 13 hub. But its not the bikes fault. These need constant maintainance.

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I have exploded a rear hub myself and its not a good feeling for sure. A couple of tips:

Use red lock-tight on the threads and beveled area where the bolts contact the sprocket. I've never had any come loose after using this method.

Be sure that you aren't running your chain too tight and putting added pressure on your hub.

I had something similar happen to my '04, I will admit it was completely my lack of maintaining the hub/sprocket set that lead to its demise. I now use blue locktite or a Caterpillar product a friend gave me from his work which also works great. I haven't had any issues using the blue in the way you have mentioned.

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yeah thanks guys, no doubt I was at fault somewhere. Never had anything like it before. Think I may have over tightened some in an effort to stop them coming loose. Also maybe the rental sprocket didn't have quite the same bevels making it hard to keep then tight?

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Another common mistake is undertightening them because you're using the Allen head side to tighten them vs the back-side nut on washer method!

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Yes. As above states, use the 14 mm. It takes me abt 10 sec and u get a gd feel of how tight they shd b. they usually set and quit loosening a few rides into a new sprocket but make it part of ur preride

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