Hub Failure Issue



21 replies to this topic
  • scottzx7rr

Posted December 26, 2000 - 06:05 AM

#1

Dumb Suggestions and don't want to offend but somthing that I have been hearing alot about the hub failure problem. Me from a roadracing background might have a suggestions that might get shot down but thought I would throw it out. As anyone around roadracing knows everything on the bike nut and bolt wise has to be safety wired. I was looking at the bolts on my YZ sprocket/hub and they have enough thread on them to be safety wired and might reduce this from this problem from happening. Also some manufacturers sell kits that make it a breeze and would reduce the time needed to do the wire job be not having to drill the bolts for the wiring.

Just my $.02 worth.

------------------
Scott #431
Some Fear Racing "Cause if you don't have any you ain't going fast enough"
'99 YZ400F(Coming to a Theater near you soon)
'92 ZX-7R and '97 ZX-7RR
"Doesn't hurt till the bone is exposed"
"When cut do you bleed green? I do!"
Pics

[This message has been edited by scottzx7rr (edited 12-26-2000).]

  • dirtdad

Posted December 26, 2000 - 08:19 AM

#2

Scott, I too have read the countless comments on hub failures and complaints on how YAMAHA has bread a weak link into the 426 in that the sprocket comes loose. Your idea is a very good one but, one common thread in all these complaints is that I don't hear mention of how often these guys with failures check their sprocket bolts! This is an item that should be checked after each ride. I know other's have mentioned this and the few that read their service manual know this also. Maybe those that are still riding on the stock hub could share with those that aren't, their "secret" in keeping these "failure prone" parts trouble free! Again, your idea is probably a good one but I think that the people that pay attention to their bike and check it over routinely will be the only ones interested in looking into that. Just my to scents.


------------------
like a kid again, 00426

[This message has been edited by dirtdad (edited 12-26-2000).]

  • scottzx7rr

Posted December 26, 2000 - 09:14 AM

#3

I agree with ya about maintanance. I am always working on my bikes. My wife thinks that I am crazy. I get a new bike and totally disassemble it. After every race change oil/plugs(on my two stroke), lube the linkage, and clean the filter atleast but normally more. I check my spokes, sprocket bolts, and all the bolts. But I came from the factory roadracing team in Japan that totally took the machine apart. So for me it is natural to do everything after a ride.

I have a friend that has a moto if you go ride with him. A fully Prepped Bike. He comes to ride and not work on others bikes along the trail. Bill is such a hard nose. LOL

But I am the same way. Preventive is so easier than repair maintanance. LOL

------------------
Scott #431
Some Fear Racing "Cause if you don't have any you ain't going fast enough"
'99 YZ400F(Coming to a Theater near you soon)
'92 ZX-7R and '97 ZX-7RR
"Doesn't hurt till the bone is exposed"
"When cut do you bleed green? I do!"
Pics

  • Guest_Guest_*

Posted December 26, 2000 - 03:47 PM

#4

I just want to comment that it's my opinion that the rear hub/sprocket may be a weak link. After my hub broke, I checked in the archives and found that this is a very common problem. I spoke to a number of different guys at my local Yamaha shop and everyone I talked to knows someone that experienced some type of sprocket/hub failure. I don't believe that lack of or poor maintenance is the common factor. I can tell you with all honesty that I'm very anal about prepping my bike, yet problems do happen. I found loose sprockets bolts and replaced them with new ones (I've heard that once locking nuts come loose they should be replaced) and still had the sprocket come loose after only a few laps.
What about the numerous clutch failures ? You can't tell me that "proper maintenance" will elminate clutch failures ? I haven't experienced clutch problems yet (knock on wood) but if and when I do have a problem I know it won't be because I've neglected to maintain it.
I just don't feel that making a general statement that proper maintenance would have eliminated a failure when it appears that more than just a couple of people from this website alone have experienced the same problem.
OK, I'm done venting now...... :)
L8tr,
CJF

  • dirtdad

Posted December 26, 2000 - 08:15 PM

#5

CJF, My apologies for offending! I don't think I said that proper maintenance is the end all to every problem on any particular bike. Most of these problems are not exclusive only to the YZ426 though! I don't expect mine to last forever either. It is a race bike though like other race bikes and they all require more meticulous maintaining than a trail/play bike. That's all I was implying! I've noticed that alot of guys don't even read their service manual. It is fairly common knowledge that the stock sprocket/chain are crap (as they are on most bikes), that's why there's such a huge aftermarket offering. This bike also has gobs of torque so something has to give. I don't believe that the stock hub is the weak link but when lesser parts (chain/sprocket) fail then something else has to give somewhere. Again, my apologies for offending. That was not my intent!

  • Scott_F

Posted December 26, 2000 - 09:43 PM

#6

While loose and/or missing sprocket bolts no doubt play a part in this hubbub, I have to say there is much more to it.

I have been racing for 25 years and have never broke or damaged a hub before, yet I exploded mine. I was using high quality and expensive chain and sprockets. In fact, they were new, so I was doubly pissed that I had to replace them also. I have never heard of any other modern MX bike that had a chronic rear hub problem. If the hub failures are much more rare with the 125 and 250, then maybe the torque does play a part. If so, then Yamaha should replace all of the damaged ones, since the sprocket flange is underdesigned for the YZ426F.

  • motoman393

Posted December 26, 2000 - 10:00 PM

#7

do aftermarket hubs like the talon's have this shattering problem? I better get me some talons and quick! lol

Garrett

------------------
I get my kicks on a 2001' YZ426!
Friendswood, TX

  • Boit

Posted December 27, 2000 - 12:27 AM

#8

I bit the bullet and shelled out for the Talon/Excel/Buchanan wheel sets. It doesn't hurt that these wheels also look great....and thanks for the info on the Moose shift lever.

  • Boomer

Posted December 27, 2000 - 04:21 AM

#9

BY NOW IT IS OBVIOUS - YAMAHA TOOK SHORTCUTS; The carb/displacement revision & debug; the Finite Element Analysis (FEA) work for the clutch componentry, as well as the drive-line components, were not completed. It is a gamble they made in their rush to win and sustain the showroom floor battle, and we are the recipients of the bike's shortcommings. A huge disappointment for many of us.

I have had only Yamaha's - in fact, I still have my '93 250 - I've never checked the hub/sprocket bolts- only when replacing those parts. I have a 1983 490 - no problems - EVER.

Sort of tuff for those raising a family to plunk down big $$$$$ then find out what we sought is not what we got. Lucky me, I'm makin' payments.

For evry person entitled to such, a class action would have to be pursued in order to have Yamaha issue a recall - it can be done.

Good luck to all.

Boomer

  • DaveJ

Posted December 27, 2000 - 11:56 AM

#10

Yikes! More hub stuff.

We'll....I guess I'll jump in.

On my new bike, the sprocket bolts always came loose. Blue loctite didn't work, red did.

Then one day, after about 5 minutes of riding, I lost three bolts. The remaining stress on the other three was too great and the hub came apart.

I ended the day with a twisted sprocket that had half a hub attached to it. The rest of the hub still had three well-preserved boltholes. This got me thinking.


So my list of what could have caused the hub failure looked like this.

1. The hub was poorly casted.

2. The hub was under designed and somehow survived all my previous beatings.

3. The bolts snapped because the bolts were too weak, but they too somehow survived all my previous beatings.

4. The bolts went from fully torqued and locked to so loose they just fell off, in about five minutes of riding.

5. The sprocket broke, (it was in two pieces) and this caused the hub to be over stressed.

6. Something got stuck in the chain.

7. Really loose spokes, or the wheel moved…dramatically.

8. Chain too tight.

9. An overly hard landing (I was doing some significant jumping at the time this happened).

Since the bike gets washed and thoroughly checked over after each ride, most of the maintenance stuff was eliminated.

I had a metallurgist examined the hub. He determined that the casting was not at fault.

Didn't think at the time to go back and try to find any of the missing three bolts. So not much conclusion could be made on those. The other three still on the sprocket, where in great shape, and the nuts were hard to remove due to all the loctite that I had put on them. So I really doubt they came loose.

As for the sprocket, the one section without the bolts still attached to it was “dished”. Meaning this part was peeled away from the hub - obviously without the bolts since the corresponding section of the hub was not broken.

This meant that either the bolts just snapped, (i.e., weak bolts) or the sprocket was pulled so hard outward that the bolts had to give and the remaining section of the hub couldn't take it anymore.

Operating like a forensic scientist, I reassembled the bike with a new sprocket, hub, and chain, without any other changes to the bike.

I disconnected the shock, raised the swing arm, and found my answer. The chain was so tight at the point where the wheel axle is level with the swing arm pivot that it wanted to pull the sprocket outward from the hub. In other words, the first thing to give from a chain being too tight is a sprocket that wants to bow outward.

So I reviewed my maintenance notes and discovered that I had adjusted the chain before the ride in which the hub failed.

Did I make it too tight or did something shift during my ride that caused it to be too tight?

So I measured the tension and it came up at 1.6 inches - the minimum spec in the book.

However, the measurement was a tight 1.6. Which means I had to pull up hard on the chain to get to 1.6 inches. So then I readjusted the chain to a loose 1.6, or even better, 1.7, raised the swing arm, and found no tension against the chain at the longest point.

Conclusion. Chain was too tight, which pulled sprocket from hub, which then snapped bolts, which then overstressed the hub, and hub broke.

Conclusion number two. A chain setting of 1.6 is just too close for comfort, and that minor movements in the wheel can make a big difference in chain tension.


Do I claim that all hub failures on the 400/426 are caused by the same problem?

No. However, when an overly tight chain is the case, the evidence is very very clear.

1. Once tight missing bolts.

2. Bolts and parts of the hub still firmly attached to sprocket, and

3. Undamaged boltholes still on the hub.

Other possibilities and thoughts?

*A casting failure or a weak hub would have very different evidence.

*Weak bolt designs would break often, for all of us.

*Bolts that loosen up, loosen together which make a lot of noise long before they present enough of a problem to break a hub. Or at least, this was my case during my early days of ownership.

So…that’s my story.

Now a days, with a new factory hub in place, I’ve put on another 60 or so hours on the bike. Everything from SuperCross to Freestyle stuff with no problems what so ever from the rear-end. And of course, a chain setting at or above 1.7 inches.

Other than that, keep in mind that stuff like this is too complex for the customer service reps at Yamaha. Perhaps a properly focused message delivered to the right person is what is needed at this point.

Hope this helps.

DaveJ

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Guest_Guest_*

Posted December 28, 2000 - 07:46 AM

#11

Dirtdad,
Apology not required ! I was just a little frustrated and vented a little at your expense.......I should apologize to you.
Your response however was basically the same response I got from Yamaha. Although most (at my local Yamaha shop)are aware of the problem, it never gets addressed and the owner is accused of poor maintenance without question. DaveJ has done a lot of homework on this particular issue and it's a shame that Yamaha doesn't have the same initiative to investigate and try to resolve what appears to be a common "problem".
With any luck I'll pick up my wheel today and reassemble my bike to go riding this weekend. The only problem now is I'll be busy thinking about my sprocket coming apart rather than gassing it over the big jumps. I enjoy my 426 but I can't afford to doubt my bikes reliablity while I'm trying to go fast around a track. What's next...my clutch ? Love my 426, but the love is beginning to fade. :)
C-Ya,
CJF

  • scottzx7rr

Posted December 28, 2000 - 08:16 AM

#12

I agree with ya CJF that it should be addressed. My KX could loosen up three out of the six bolts and be fine. I also hope that you didn't think I was meaning it was caused by poor maintanance. I was saying to maybe reduce the chance of it happening. I was just saying that maintanance should be a important element to riding any bike.

Probably a silly question but after reading DaveJ post would it be safe to say that it might be safer to have a slighty looser chain or to check the whole chain to find the tight spot and adjust there instead of anywhere.

------------------
Scott #431
Some Fear Racing "Cause if you don't have any you ain't going fast enough"
'99 YZ400F(Coming to a Theater near you soon)
'92 ZX-7R and '97 ZX-7RR
"Doesn't hurt till the bone is exposed"
"When cut do you bleed green? I do!"
Pics

  • AngryCandy

Posted December 28, 2000 - 08:18 AM

#13

DaveJ,

Excellent investigative work, and I must say, I am very impressed that you keep a log of every maintenance item performed...even the level of adjustment of the chain!!

My 98 400F has never shattered a hub, nor has any of the sprocket bolts come loose, but I do not jump it the way some of you do, and I always shoot for a chain adjustment in the center of the recommended range (1.8 inches.)

It seems to me that in a situation as described, there is a very fine line between having a chain with the ability to stretch ever so slightly to avoid the hub failure, and having a chain that stretches too much and needing adjustment and replacement too frequently. Perhaps the manufacturers are making chains with a tensile strengths too high for this application. I know that everyone wants the maximum life out of a chain, but I, for one, would gladly buy a new chain every once in a while for the peace of mind in knowing that the entire rear will not grenade on me.

For those that have had this unfortunate accident happen, what kind of chain and chain rating were you running?

(PS. I am not attempting to shift any of the blame from Yamaha, but this may be the reason they come with such crappy chains :) )

[This message has been edited by AngryCandy (edited 12-28-2000).]

  • Scott_F

Posted December 28, 2000 - 09:09 AM

#14

That's a funny thought. I wonder if anyone broke their hub with the stock chain? I was running a new, expensive, high quality RK chain, and new AFAM sprockets. And I do run my chains on the loose side. People often point out that my chain looks loose.

  • DaveJ

Posted December 28, 2000 - 09:23 AM

#15

At the time I broke mine, I was running a 51 tooth Renthal with HD DID chain, and I do agree that this contributes to the problem.

Not to make any conclusions, but it is rather interesting how even the slightest modifications to motos and cars can open up a host of problems.

  • dirtdad

Posted December 28, 2000 - 01:36 PM

#16

Davej, excellent thread!! This is why I read these posts. I'm 40, have been riding, watching, reading everything about these things and I'm still learning. CJF, that is my intention when I respond or initiate a post. Only to share or receive info/ideas. Everyone in this post has a very good point. I'm certainly not championing YAMAHA. I happen to really like the bike though. As I said before, it's nothing like what I'm used to, problems aside. No need to apologize to me though. I'm very thick skinned! Please keep the comments coming.
Again Davej, great reply! You sound like an engineer. Ask one what time it is and they'll tell you how to build a clock! Anyway, there is obviously a limit to how much "slack" you should leave in the chain after adjustment. What do you feel is a safe range after your in depth testing? I'll definitely keep your findings in mind when I adjust mine.
Urb

------------------
like a kid again, 00426

[This message has been edited by dirtdad (edited 12-28-2000).]

  • blbainb

Posted December 28, 2000 - 07:07 PM

#17

This is interesting reading. I've heard mention of the hub problem but never experienced it myself ('99 400, '00 426, '01 426). These bikes have been very reliable for me although I do seem to have a defective carb on the '01.

I appreciate the investigation on the possible causes for the hub failures. Over the last couple of years I've noted that if I try to set the chain slack to anything less than the maximum value of the range specified in the manual (1.6-2.0") then the chain will quickly 'stretch' to the 2.0" value. Now I try to keep the chain slack at 2.0" or even a bit more and have found that the chain/sprocket lasts much longer.
Funny thing though, I would expect there to be not only hub failures but also countershaft seal failures if the chain slack was the culprit.

  • st400f

Posted December 29, 2000 - 12:27 AM

#18

i too have had a rear hub and sprocket come apart on my 99 400 f i was guilty of poor spoke maintnance wich i believe lead to the failure since my rear wheel rebiuld i have kept the spokes tight and have had no problems with the sproket bolts coming loose i wounder if everyone who had a failure, did it start with loose sprocket bolts?

  • dirtdad

Posted December 29, 2000 - 07:45 AM

#19

For those of you out there who have experienced hub failure; What is your riding level? Maintenance/parts issues aside, I think alot of us aren't at the pro-level yet.
I've been out of racing for a very long time and at my age I don't think I'll be threatening Mcgrath and the boys but, I hope to be stressing this bike after a while. I'd like to take as much info from this forum so I can keep it running without having to lay down the $$$ for a Talon or equivelent hub! It sounds to me like some of you have done your homework (stood back and looked things over beyond what the book says or what you were used to) and come up with some very simple yet effective solutions! These may not be the answers to everyones hub problems but it should have all our wheels turning so to speak (no pun intented). Thanks for the info and my apologies for the long winded note!

Urb

------------------
like a kid again, 00426

  • Scott_F

Posted December 29, 2000 - 09:17 PM

#20

I'm a Senior Expert level rider, and did countless 90-100' jumps on my 426. I thank God that it didn't blow when I landed one of those. I was doing a small step up jump, and landed on the face with low rpms and lots of throttle. This put a heavy torque load on the hub, and it shattered around the flange.





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