Broken hubs

I've seen a few people breaking hubs on the 06 450s. Just curious if anyone has an old broken hub laying around that they are willing to donate. You can let me know through PM. I hope this post isn't breaking any rules, if it is then feel free to delete it.

I should have one in a week or so. Broke one on my 06 250. When it gets rebuilt I'll send it up to you.

Mark

I've seen a few people breaking hubs on the 06 450s. Just curious if anyone has an old broken hub laying around that they are willing to donate. You can let me know through PM. I hope this post isn't breaking any rules, if it is then feel free to delete it.

Will you lace me some wheels if I buy everything? I send ya a broken one haha for real what ya gonna do with it?

hey KJ, why the interest???? I have a broken 08 rear hub...came into the shop last week. I have seen others broke in the same fashion....sprocket ripped right off the hub because the sprocket bolts were loose. I don't know if people are just tightening the allen instead of getting a wrench on the backside nuts to properly tighten them or what. It is fairly common i guess with 06 to 08's...I have seen maybe 4 or 5 total in the past 2 years.

and it really sucks when this happens and it throws the chain through the case's.......twice!!!!!

and it really sucks when this happens and it throws the chain through the case's.......twice!!!!!

OUCH haha, i have a little carbon fiber case saver deal on my 426, dont know how good a job it would do against a flailing chain but sound like you should get one.

OUCH haha, i have a little carbon fiber case saver deal on my 426, dont know how good a job it would do against a flailing chain but sound like you should get one.

Your fancy little carbon fiber case saver will not save you. I think the case saver I had on my bike actually is the cause of my broken case. Chain broke and wedged itself between the carbon fiber case saver and the motor case.

Broken hub? I have an 05 450 that the sprocket came loose on after a 45 minute gp race, and ripped the hub apart. It was tight before the race but I didn't put any thread lock on it. So it was my fault and it will never happen again to me.

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This was debated awhile back and my theory on this has been disputed but it has worked for me. Be very careful with the torq specs on the rear sprocket. If it comes loose once or you have overtightened the bolts get new bolts set to torq and Loctite. I believe the bolts are damaged when over tightened and will continue to come loose until the slamming breaks the hub. I trashed 2 hubs on YZ250 2 strokes and had friends do them on 426s even though Loctite was used. Since following these guideline none of us has had a failure.

Thanks for the replies guys. I only need like 2 or three. I am an engineering student and am looking at failed materials and I felt that hubs would be great to look at and learn from.

This was debated awhile back and my theory on this has been disputed but it has worked for me. Be very careful with the torq specs on the rear sprocket. If it comes loose once or you have overtightened the bolts get new bolts set to torq and Loctite. I believe the bolts are damaged when over tightened and will continue to come loose until the slamming breaks the hub. I trashed 2 hubs on YZ250 2 strokes and had friends do them on 426s even though Loctite was used. Since following these guideline none of us has had a failure.

well i don't know about that, i put a new renthal alu sprocket on my bike and didn' use a torque wrench, just snugged them down fairly tight and have had 15-20 hours on my bike since its been fine.

although this thread makes me want to take it off and torque it down to specs.

Thanks for the replies guys. I only need like 2 or three. I am an engineering student and am looking at failed materials and I felt that hubs would be great to look at and learn from.

KJ790 cool project - To the Hub great debate - I would like to find out what is causing this also as I have never had a hub issue on any Yami 1997 - up.

Correct me if I am wrong but aren't these hubs made out of a composite? Magnesium/aluminum mixed together and maybe some other materials, could it be a stress failure because of the torque of the 450 coupled with a design/casting flaw? Or the metals not bonding together as uniform as they should be?

Correct me if I am wrong but aren't these hubs made out of a composite? Magnesium/aluminum mixed together and maybe some other materials,
That is called an alloy. Alloys are a blend of metals used to achieve specific metallurgical properties. Composites are composed of differing materials, such as polymer resins and glass or carbon fibers, to create new materials with properties not available in the individual components. All aluminum parts of any kind are alloyed.

In the case of the '06 hubs, there is, IMO, evidence that there was a defect in the hub castings for part of the production run. This is evident from the hubs in which the bearing pocket loosened around the bearing, indicating the metal was excessively ductile (soft). This weakness, if in fact it exists, may be a contributing factor in the failures of the hub flanges on those models. There are, I believe, other things involved, though.

This weakness, if in fact it exists, may be a contributing factor in the failures of the hub flanges on those models. There are, I believe, other things involved, though.

yea I agree 100%....it is either: or combination of

chain tension

sprocket nut/bolt torque or lack of issue

or defective casting

not to be confused with the other hub related issue

spinning bearing issue

All of which Yamaha declares there is no issue with....hmm:excuseme:

That is called an alloy. Alloys are a blend of metals used to achieve specific metallurgical properties. Composites are composed of differing materials, such as polymer resins and glass or carbon fibers, to create new materials with properties not available in the individual components. All aluminum parts of any kind are alloyed.

In the case of the '06 hubs, there is, IMO, evidence that there was a defect in the hub castings for part of the production run. This is evident from the hubs in which the bearing pocket loosened around the bearing, indicating the metal was excessively ductile (soft). This weakness, if in fact it exists, may be a contributing factor in the failures of the hub flanges on those models. There are, I believe, other things involved, though.

Well said..... Exactly what happened to mine bearing pocket loosened around bearing I caught it before disaster struck. Guys this has been said 100 million times but please loctite your sprocket bolts.

yeh, one side of my bearing pocket is loose. but im gonna still ride it. it doesnt seem like its that huge of a deal

yes well i guess the difference in a failing hub is not at the fault of yamaha or the manufacter it is ours as a community, personally i have never lossed a hub or sprockets to loose bolt/nuts and have never found mine loose, but on the other hand i have never torqed these bolts either, nor have i ever found any evidence of over torqing on the bolt or sprocket and hubs of any of my machines, i dont use the crank it till is stops method but i dont use the hand tight method either, maybe im just good at sensing the right amount or maybe im jsut lucky, or maybe god gave me the ability to troq things by feel, i can torq chevy heads bolt with a breaker bar to within 5ft.lbs everytime

I had a 2001 yz 250 and the sprocket bolts kept comeing loose. i kept tightening them more and more and useing lock tight. i could not figure out why they kept comeing loose it was makeing me mad. i even tryed diffrent locking nuts. i think the bolt getting damaged is it a good theory. but anyways after 2 weeks of messing with them i went to a race that was 3 1\2 hours away got into the first 30 seconds on the first lap in the first moto and some off a jump and soon as i landed the tire locked up. when i came to a stop (very quickly) i looked back and my sprocket had broken off the hub and folded into a 90 over the swingarm. that was a crapy day!!!!

Another thing to consider in dealing with loosening sprockets: once the whole sprocket has loosened, the bolt holes in both the hub and sprocket quickly become elongated, and even if only slightly so, will from then on allow the sprocket to scrub on the hub and work loose again. If tis gets caught before it goes too far, the sprocket and bolts can be replaced, and the hub and sprocket drilled to accept dowel pins to check the rotational slippage.

Another thing to consider in dealing with loosening sprockets: once the whole sprocket has loosened, the bolt holes in both the hub and sprocket quickly become elongated, and even if only slightly so, will from then on allow the sprocket to scrub on the hub and work loose again. If tis gets caught before it goes too far, the sprocket and bolts can be replaced, and the hub and sprocket drilled to accept dowel pins to check the rotational slippage.

In a couple hubs i have seen it is very evident the cause was loose bolts. You could visually see where a couple holes were elongated. The thing is that it only takes one or two to be loose and your having a bad day.

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