Yz450f Rear Hub Help


20 replies to this topic
  • JOHNSON017

Posted November 04, 2007 - 06:04 PM

#1

I Have A 07 Yz450f...the Other Day I Was On The Track And The Rear Sproket Broke Off The Hub And Completely Destroyed My Rear Wheel....i Heard That This Is A Common Problem With Yz450fs If The Chain Is Too Tight....can Anyone Help?

  • Ronin 26

Posted November 04, 2007 - 06:47 PM

#2

It's a common problem if the sprocket bolts come loose.....

  • todds924

Posted November 04, 2007 - 07:39 PM

#3

I Have A 07 Yz450f...the Other Day I Was On The Track And The Rear Sproket Broke Off The Hub And Completely Destroyed My Rear Wheel....i Heard That This Is A Common Problem With Yz450fs If The Chain Is Too Tight....can Anyone Help?


The nuts that hold the sprocket should be checked every race. The hubs are fine. It is because they were loose that this happened to you. I have seen it happen lots of times and not just YZ's

  • tw557

Posted November 05, 2007 - 05:22 AM

#4

I am in the same situation. My chain was DEFINATELY not to tight. I just adjusted it to the manual specs. I just checked my bolts. The reason I know is because my friend just crashed pretty hard 1 month ago as his second hub in a year broke. He was also sure it was not too tight sice we are avid TT browsers. Then while riding this WED. a new guy I met on an 07 broke his hub. I was explaining to him about this problem. I get home and wash the bike and sure enough I have a cracked off sprocket ear. All but one bolt was fully tight. The bolt one place infront of the break was a little loose. I had on an IRON MAN sprocket, my friends had on renthal and stock. The ironman could be a factor since it does not have a full inner circle. Just hard to understand since the same hub is used for the last 8 years on these bikes.

  • Ga426owner

Posted November 05, 2007 - 06:36 AM

#5

Nope...sorry to tell you that your issue is loose sprocket bolts. It makes no difference on what kind of sprocket that is used. There is a method to keeping this from happening with non stretched bolts/nuts, proper torque, loctite and enough time for loctite to set up.....and never breaking the seal until replacement
I have not had any issues with loose sprocket bolts/nuts or hubs ever....

  • tw557

Posted November 05, 2007 - 07:15 AM

#6

I really used to have the same confidence. I read manuals, read on TT and being extra concerned about safety at by older age, I thought I was good on the Hub issue. Sure I plan on the whole deal of loctight, and super good bolts and washer, but the Ironman sprocket is gonna go. I really did not give it a second thought before but my ear broke off the exact width of the sprocket foot. All the bolts including that one SNAPPED loose and had friction the whole way off. Its hard to believe that ONE loose bolt located away from the break caused this. I'm still not sure it was somewhat looser because of riding it after it broke. I have friends with 3 wr450's and an 03 and 05 yz450f with unbelievable hours with not a problem. And now 3 06-07's with less then 20 hours each with a total of 4 broken hubs. 2 (my friends second one and mine)of these hubs and chains were pretty well maintained because of previous problems. I guess just buy a new hub and do the whole locktight thing. For peice of mind I have to change something so the sprocket is for sale. Sucks for the little use after paying so much for it!!!

  • grayracer513

Posted November 05, 2007 - 10:12 AM

#7

I Have A 07 Yz450f...the Other Day I Was On The Track And The Rear Sproket Broke Off The Hub And Completely Destroyed My Rear Wheel....i Heard That This Is A Common Problem With Yz450fs If The Chain Is Too Tight....can Anyone Help?

Notwithstanding anyone's denials, it strikes me that the single most common cause of this failure is an excessively tight chain. The '06 and later YZF sets up with a looser specification than the '05 and earlier models had, and inevitably, when it's correctly adjusted, it looks too loose. The temptation to run it tighter is often overwhelming, but wrong, nevertheless. I've caught any number of guys at the track and on rides running their rear chains too tight on the late YZF's, myself.

When the chain is too tight, and the swing arm passes through the point at which all 3 centers of the output shaft, swing arm pivot, and rear axle are aligned, the chain is drawn completely taught and placed under extreme tension. The amount of force applied under these circumstances by a chain as little as 1/4" too tight is very high. At this point, something has to either flex or break, and the hub flange, being an aluminum casting, will only put up with so much flexing.

Another thing I have noticed (and this one is certain to decrease my popularity) is how many of these failures occur with Ironman sprockets. Mind you, it is not the fault of the sprocket, per se; it's still a tension issue. However, because the Ironman lacks a full ring of material at its inner diameter, it places a more localized stress on the mounting lugs of the hub if and when it is pulled over by an excessively tight chain. Choosing another sprocket besides an Ironman isn't the cure, because they arten't the cause. They're just more apt to break the hub under these circumstances.

As to bolts coming loose, I have to say that based on my experience, that isn't the problem. None of the 25 YZF rear sprocket bolts I currently own or have over the past 10 years have ever loosened, in spite of a complete lack of thread locking compounds, and in spite of reusing the same lock nuts when changing sprockets. Given that, I don't see a problem there. I have encountered many rear hubs over the years on which the sprocket was run loose for a while, and the bolt holes beaten oblong. None of these, except for one, broke, and I saved the unbroken ones by pinning the sprockets to the hub. The broken one lost a mounting lug, but that was all.

So, with all of that, and my experience in failure analysis, my conclusion is that incorrect chain tension is the root cause of at least the majority of such hub failures on late YZF's. The only thing that, IMO, mitigates that to any extent is that there were some '06 hubs that experienced drive side bearing pocket loosening. But, unless there was an intrinsic weakness in the casting or materials used, that failure could just as easily have been put down to chain tension as well. As I said, something has to give.

  • TobyB

Posted March 31, 2008 - 08:41 PM

#8

I have just had the same failure with the Ironman Sprocket and I think that my chain was probably too tight. I think that my bolts must have come loose also because the three holes still left on the hub have no bolts in them. The only bolts I have left are the three still attached to the sprocket with parts of my hub. Grayracer, what brand of sprocket do you use and number of teeth, if you dont mind me asking. Also, should I go with a stock hub or a different brand and money IS a issue.
Thanks for any advice
Toby

  • rickallen124

Posted April 01, 2008 - 01:44 AM

#9

Stock is the cheapest. I believe that you can get the stock hubs for around $70 a piece. Of couurse you'll need bearings, seals and spacers. Talon, TCR and Excel may be a little stronger but they are at least 4 times the cost.

  • grayracer513

Posted April 01, 2008 - 10:38 AM

#10

Grayracer, what brand of sprocket do you use and number of teeth, if you dont mind me asking. Also, should I go with a stock hub or a different brand and money IS a issue.

If, as I suspect, the hub broke off at the sprocket flange outside the spoke line, and you were lucky enough to have no spokes damaged in the mishap, re-lace a stock hub to it. OEM is the least expensive option in any case.

I like Tag Metals rear sprockets. They are light, hard anodized so they wear very well, as aluminum goes, and are reasonably priced. Up front, any quality sprocket is OK with me, and the last one I ordered was a Pro Taper, based on price. I like a 13/48 setup right now, but I don't do SX, either, only outdoor tracks and mostly desert.

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  • TobyB

Posted April 01, 2008 - 10:51 AM

#11

Thanks for the info.
Toby

  • Wiz636

Posted April 01, 2008 - 02:01 PM

#12

I just put an Ironman sprocket on my '06 and when mounting it I was a little concerned about the lack of an inner ring. Seems like there could be a better option for saving a few ounces. That being said, I wasn't concerned enough with it to not put it on. I have always run my chain slack at the very loose end of the spec and I use a torque wrench on the sprocket bolts along with red loctite so I don't forsee any issues..

  • TobyB

Posted April 01, 2008 - 04:19 PM

#13

I also torqued my sprocket bolts and used the red loctite. Watch the bolts very close (after EVERY ride.)
Toby

  • BlownCobra

Posted April 02, 2008 - 01:31 PM

#14

I also torqued my sprocket bolts and used the red loctite. Watch the bolts very close (after EVERY ride.)
Toby


+1

In fact, I use a Sharpie marker and draw a line on each sprocket bolt to the sprocket. I can visually see if the bolts have backed off. Before I get on the bike I give it a quick glance. If you notice one is loose, you need to clean the threads and reapply loctite.

FWIW - When I replace the sprocket I use new sprocket bolts.

  • steve_97060

Posted April 02, 2008 - 03:06 PM

#15

+1

In fact, I use a Sharpie marker and draw a line on each sprocket bolt to the sprocket. I can visually see if the bolts have backed off. Before I get on the bike I give it a quick glance. If you notice one is loose, you need to clean the threads and reapply loctite.

FWIW - When I replace the sprocket I use new sprocket bolts.


good idea, i think i'll use the sharpie when i install my new sprockets...

  • TobyB

Posted April 02, 2008 - 03:39 PM

#16

good idea, i think i'll use the sharpie when i install my new sprockets...


I second that, great idea.
Toby

  • Swank198

Posted November 20, 2008 - 05:07 PM

#17

Well i looked this problem up because last night i was at the track and this happend to me....the damage was unbelieveable....

I ride a 2007 CRF 450 and i love it. I check the sprocket every ride because i am aware of this through experience. I have been riding for years and this has never happend to me....only buddies that i watch stress and think to myself...damn i hope that never happens to me....

I hit a simple tabletop that was about 90 ft with a good run, landed on the gas on the down side and as soon as the bike hooked up the bolts ripped all the ears off my hub, dropped the sprocket down, destroyed my chain guide rail, ripped the bracket almost completely off my swing arm, and sheered all the teeth off my front sprocket. I run a renthal chain, a renthal sprocket and they both were the only 2 things that didn't suffer sufficent damage.

The idea about the sharpie is GREAT and the locktite is a must...

If anyone has any other ideas about this please share....the money this is costing me may end in costing me this entire series....:thumbsup:

Thanks guys,

Swank

  • grayracer513

Posted November 20, 2008 - 06:14 PM

#18

If anyone has any other ideas about this please share....

You did read my post on the subject, yes?

  • wheeldude

Posted November 21, 2008 - 03:57 AM

#19

Hey guys, I build quite a few wheels and have a couple of thoughts on Ironman and Vortex sprockets. I see quite a few hubs that are worn on the inner ring where the sprocket mounts. Because there is no full cicle contact on the inside of the sprocket, the hubs wear even with tight sprocket bolts and correct chain adjustment. There just is not enough contact area IMO to support the torque the Modern 4 strokes have. Of course, the faster the rider, the quicker the hub wears. I now only run sprockets with full inner contact. Just my 2cents. WD

  • Ga450owner

Posted November 21, 2008 - 06:17 AM

#20

Not again....oh I see an old thread ....:thumbsup:

I agree more contact can be a better thing........but I have only used Ironman sprockets since they came out and I have never had a hub blow out.
I believe it is all in how you mount the sprockets, using non stressed sprocket bolts and nuts, use the correct loctite and most importantly - let the stuff set up for 24hrs before riding oh and yes never never make the chain tension too tight.

I know of many honda riders that switched to Yami sprocket bolts





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