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Sylvain

Oups! Rear sprocket tearinf off the hub

14 posts in this topic

Hy everyone !

I just had a mishap with my wr. While landing from a modest jump I felt the rear wheel locking up and a clunking noise. The rear sprocket teared off from the hub detroying the hub flanges in the process. All the bolts were gone and the holes in the hub are ovalised. A new hub is on order with new bolts kit. $160,00 for the hub, $60.00 for the bolt kit and a couple hours (at $50,00/hres) for relacing the wheel. With all the taxes it will come around $400.00 cdn for this episode.

The part guy at my dealer tells me that this type of breakage is very rare :thumbsup:. . The sprocket was folded and the hub destroyed. I checked the bolts' torque regularly. Is there anything else that can be done to prevent this in the futur ?

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A result of the bolts coming lose. Once that happens, its only a matter of time before the hub is ripped apart by the brute torque of these things.

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my friend with an XR650 just had the same problem, only he was climbing a hill. it was caused by the rear sprocket bolts, too. his chain bunched up at the countershaft and destroyed his case, along with the rear hub.

its warrantied so the parts are free, but he has to pay for all the labor at a honda dealership. $900 at least. the parts alone would cost around $850 anyway.

freak failures happen, sometimes catastrophic. i dont think you can prevent this kind of thing. :devil:

he had just "tightened" the bolts the day before, too. i locktite them and are all are probably too tight. they will snap in half before they come loose. :thumbsup:

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Yup,

Ya cant put enough loctite on those babies !!!!

Theres a fair bit of force trying to undo them so glue em and torque em well.

Deano

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You are not alone.

After a recent 2 hour hare scrambles, all the sprocket bolts were loose and one broke when I put wrench on it.

I was really close to where you ended up. I will regularly check them from now on.

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I have written about this problem in the past. I have destoryed 2 rear hubs, 1 on a 99 YZ250 and 1 on a 02 YZ250. Several friends have done the same on various bikes and we came to the following, and none have had a failure since.

When the bolts come loose 1 time they stretch. You will never be able to get them to hold the torq settings again. You can loctite them all you want but the metal in the bolt is fatigued and it will continue to stretch never staying tight.

When your bike is new take all the bolts out and loctite them. Don't over torq, ever. If the bolts ever do come loose, replace them (the old nuts can be used).

Good luck!

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Thanks for the tip.

I just finished putting the rear wheel back on the bike. As you specify, I applied the proper torque and loctite the new bolts. I didn't have the choice since all the bolts snapped from the hub. :thumbsup:.

I beleive this is where a dealer can steal money from us. Specially when you consider that the hub assembly was $160.00 cdn !!! Which is not too bad, but for 6 bolts + 6 nuts and 6 washers cost me near $ 50.00 cdn, again :awww:. I don't get it :lol:. The bolts must be made from the same material as the space shuttle :devil:.

I will make it a routine maintenance to check the torque on those bolt.

Thanks :D

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I was wondering if running a chain too tight might precipatate some of these sprocket failures?

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I was wondering if running a chain too tight might precipatate some of these sprocket failures?

It can, hopefully the master link will break first though with that type of pressure put on the drive system. If the bike has loose sproket bolts the masterlink isn't the weak link any longer. Once the bolts become loose and stretch then the bolts become the weak link, even if tightened.

A to tight chain was one of the things considered when we brain stormed the problem.

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Hiya,

The other obvious choice is to lock wire them after you have torqued them up correctly, that way they are there to stay till you cut the wire. Would take a bit of fiddling in drilling the holes but if its a constant problem, this would fix it.

Dean

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I was wondering about those sprocket bolts.

Are they a one time affair ?

Meaning that when they have been "properly" torqued, can they be reused ?

I applied the blue Loctite which is medium strenght. If during a routine inspection with the torque wrench I find that they have loosen, can we just clean and use high strenght loctite ? Or do I still have to dig in my pocket for new botls ?

Thanks

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You can use the sproket bolts until they become loose during a ride and are subject to the stress of being loose under power. Just clean them up and retorq when putting on new sprokets or what ever.

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