Cracked rear hub???? Tech help please**

BevoDave
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BevoDave
Edited Date/Time 1/27/2012 2:29pm
My buddy's 2007 CRF450's rear hub sheared off at the track today.

Upon closer inspection, it appears the rear hub cracked under torque, causing the sprocket to literally fall off the hub. The hub is cracked/broken where it meets the sprocket.

The sprocket bolts were set and torqued recently with lock-tite, the chain tension adjusted properly, axle tight etc.

Ironically, a KTM had the same thing happen tonight as well.

Did Japan change hub casting vendors? Is this a new phenomenon?

My question is this....Has this happened to you?
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williamsmotowerx 7/30/2008 12:25am
7/30/2008 12:25am
What kind of sprocket and material?

I've seen it happen.. but it was because sprocket was worn where tapered portion of bolts head goes through
FGR01
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FGR01 7/30/2008 12:49am
7/30/2008 12:49am Edited Date/Time 7/30/2008 12:50am
Seen it happen fairly regularly on Yamahas, not so much on Hondas. Loose sprocket bolts or a misaligned chain can contribute. Also snapping the throttle on real hard or landing with the gas wide open into a high-traction situation doesn't help.

Honda sells the entire hub as an assy. complete with bearings and seals already installed. The price is reasonable, unlike some other companies' parts.
Motodrew295
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Motodrew295 7/30/2008 1:34am
7/30/2008 1:34am
I loctite and tourque my bolts. It seems they come loose every other ride. The bolts oval out the hub, I may do like a friend of mine and get bigger bolts and drill out the holes in the sproket.
kawboy388
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kawboy388 7/30/2008 4:20am
7/30/2008 4:20am Edited Date/Time 7/30/2008 4:20am
I broke a sprocket bolt ear off my KX450 hub while torqueing it down. If you don't want to go with the stock one the RAD econo is a good choice for about $240. It's the exact hub as their Eagle, but it doesn't have the weight saving holes machined into the side.

The Shop

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catatonic
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catatonic 7/30/2008 4:41am
7/30/2008 4:41am
It happens more than it should on KTM's.
Even the smallest spode whips will wreck hubs if you dont get the bike straight again before landing.
I've also been told to avoid using sprockets that only meet the hub at the mounting bolt point because it puts more stress on the hub than a sprocket that seats against the entire hub.
crowe176
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crowe176 7/30/2008 7:18am
7/30/2008 7:18am
07 yz450, twice. First running an Ironman sprocket (twisted like a pretzel around the swingarm), second was a sunline sprocket. Both locktite/torqued.
gp
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gp 7/30/2008 7:42am
7/30/2008 7:42am
KTM's need a very loose chain. If it's too tight it will crack the hub. Been there done that. By the way I have two, count them two 19 inch rear wheels for a KTM. They do have bad hubs but the rims and spokes are good if anyone can use them. Slight fee of course.
partialperson
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partialperson 7/30/2008 7:43am
7/30/2008 7:43am Edited Date/Time 4/16/2016 7:50pm
I had this happen on our '05 YZ250 when it was brand new. Within a year i knew of 8 others with the same situation. This may sound stupid but it works. Many years ago while competing with the family sprint car runnig WoO, AllStar & chasing money races we had a situation with wing bolts backing off or losing their torque. We tried every form of bolt,nut, Loctite, sealers, glues to no avail. Common 100% pure household clear silicone lathered on nicely ended up being end of all frustration. I use it on my sprocket bolts, wiping around the contact bevel, contact shoulder where it meets the hub & even spread a little down onto the threads. I haven't had an issue since, along with the many others I've been in contact with that chose to use this method.
partialperson
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partialperson 7/30/2008 7:45am
7/30/2008 7:45am
Hey GP, I was just looking through some old photo's on your site. I'll be putting together an order soon.
partialperson
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partialperson 7/30/2008 7:51am
7/30/2008 7:51am Edited Date/Time 4/16/2016 7:50pm
Oh yeah, I was thinking the bolt shoulders have a bit to much clearance in the hubs. Stick the bolt in the hub without sprocket, the shoulders don't seem to snug. The silicone fills the gap. i believe that's was also the case on the wings, aircraft quality bolts & heim joints but enough clearance to allow torsional vibration to do damage. I may be wrong about the reasoning, I'm Ok with being wrong, but I know what worked.
Matt Fisher 7/30/2008 8:30am
7/30/2008 8:30am
So you're suggesting that the bolt be totally covered in silicone, not just adding a dab after it's been torqued down?
Gonzo0100
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Gonzo0100 7/30/2008 8:42am
7/30/2008 8:42am
Oh Hell Yes, my sprocket bolts on my 06 CRf250 go loose after a day of moto. I tried Blue loctite... came loose... I tried red... got loose (not as bad). Now I just red them and check them multiple times during the day (after every moto).
CRF122
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CRF122 7/30/2008 10:26am
7/30/2008 10:26am
crowe176 wrote:
07 yz450, twice. First running an Ironman sprocket (twisted like a pretzel around the swingarm), second was a sunline sprocket. Both locktite/torqued.
06 yz450 twice! Both aluminum sprockets, bolts to spec, chain to spec on first, and looser(recommended) on the second. The second time it happened I went straight to Yamaha and they handled it, no problems including labor.

i was not suprised to see the revised rear end on the 09's
FGR01
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FGR01 7/30/2008 10:41am
7/30/2008 10:41am
kawboy388 wrote:
I broke a sprocket bolt ear off my KX450 hub while torqueing it down. If you don't want to go with the stock one the RAD...
I broke a sprocket bolt ear off my KX450 hub while torqueing it down. If you don't want to go with the stock one the RAD econo is a good choice for about $240. It's the exact hub as their Eagle, but it doesn't have the weight saving holes machined into the side.
That's about 2x what a stock Honda hub from Service Honda costs.
navce78
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navce78 7/30/2008 1:37pm
7/30/2008 1:37pm
got the same prob in my KX250

my sprocket teared into many pieces

got my hub fixed and now I chek the bolts every after moto

they seem to come loose with the torque, even if you loctite them
aggiemoto99
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aggiemoto99 7/30/2008 1:42pm
7/30/2008 1:42pm
had it happen two different bikes.

Sprocket bolts get loose, boom. breaks.

So I get new bolts and nuts every time I do a sprocket, and I snug them all, tighten them all, then pull one nut at a time and locktite it while the others are tight until every nut has locktite.

Seems to have worked ever since, no failures to date, knock on wood. but I check the bolts every ride, just to make sure.
babba boey
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babba boey 7/30/2008 2:32pm
7/30/2008 2:32pm
It is very important to tighten rear sprocket bolts in a cris cross pattern. I do this and in 20 years of riding and racing, I have not had a problem.
Tiki
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Tiki 7/30/2008 5:51pm
7/30/2008 5:51pm
babba boey wrote:
It is very important to tighten rear sprocket bolts in a cris cross pattern. I do this and in 20 years of riding and racing, I...
It is very important to tighten rear sprocket bolts in a cris cross pattern. I do this and in 20 years of riding and racing, I have not had a problem.

Pit Row

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KTM boy 137
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KTM boy 137 7/30/2008 6:19pm
7/30/2008 6:19pm
Had it happen once on my KTM250sx.

SPYGUY used to say he'd never heard of such a thing with other brands... clearly that's not the case.
Trip
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Trip 7/30/2008 6:26pm
7/30/2008 6:26pm Edited Date/Time 4/16/2016 7:50pm
Happened to me about a year ago. Sprocket came loose and ripped the hub apart. 05 Yamaha YZ450



Williamson425 7/30/2008 6:52pm
7/30/2008 6:52pm
I did it once on a yz250f. Im pretty sure something came loose first though.
rubarb
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rubarb 7/30/2008 7:07pm
7/30/2008 7:07pm
KTM boy 137 wrote:
Had it happen once on my KTM250sx.

SPYGUY used to say he'd never heard of such a thing with other brands... clearly that's not the case.
Was the nose ring ok afterwards?
gp
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gp 7/30/2008 7:15pm
7/30/2008 7:15pm
Did the second one on my KTM 250sx with a Vortex sprocket. The inside of the sprocket didn't have a complete ring. I knew putting it on that it was a bad design.

The first KTM hub cracked inside the hub, the sprocket was not the problem there.


Darn it.
partialperson
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partialperson 7/30/2008 8:01pm
7/30/2008 8:01pm Edited Date/Time 4/16/2016 7:50pm
Matt Fisher wrote:
So you're suggesting that the bolt be totally covered in silicone, not just adding a dab after it's been torqued down?
Yeah, squirt out a line & spread it around, wipe off the excess after tightening bolts. I have yet to have anyone tell me this method didn't work for them.
Soxfan24
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Soxfan24 7/30/2008 8:39pm
7/30/2008 8:39pm
Happened to me last year, 2007 yz250f. It did make a cool noise in the air when it happened though.


todder
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todder 7/30/2008 8:44pm
7/30/2008 8:44pm
Use green Loctite stud and bearing retainer, stronger than red.
babba boey
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babba boey 7/30/2008 8:45pm
7/30/2008 8:45pm
gp wrote:
Did the second one on my KTM 250sx with a Vortex sprocket. The inside of the sprocket didn't have a complete ring. I knew putting it...
Did the second one on my KTM 250sx with a Vortex sprocket. The inside of the sprocket didn't have a complete ring. I knew putting it on that it was a bad design.

The first KTM hub cracked inside the hub, the sprocket was not the problem there.


Darn it.
I have been running Vortex sprockets for years. Never had a problem but it is important to tighten down bolts in a cris cross pattern.
BevoDave
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BevoDave 7/30/2008 10:19pm
7/30/2008 10:19pm
Trip and Soxfan, those pictures are exactly what his looked like. Same place on the hub, with the break in the same direction.

It's starting to sound like it is common and the only way to prevent it is to check them regularly and use green lock-tite.

I just checked mine!

Appreciate the help fellas.

Moto on!
Filme
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Filme 7/30/2008 10:31pm
7/30/2008 10:31pm
If you are wanting to get a good replacement hub/wheel set, go and check out Faster USA who specialize in wheels and hubs. Their pricing is very competitive and the service they provide is awesome.

http://www.fasterusa.com
CamP
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CamP 7/31/2008 3:39am
7/31/2008 3:39am
BevoDave wrote:
Trip and Soxfan, those pictures are exactly what his looked like. Same place on the hub, with the break in the same direction. It's starting to...
Trip and Soxfan, those pictures are exactly what his looked like. Same place on the hub, with the break in the same direction.

It's starting to sound like it is common and the only way to prevent it is to check them regularly and use green lock-tite.

I just checked mine!

Appreciate the help fellas.

Moto on!
The only way to prevent this is to not let your sprocket bolts get loose in the first place. Once the bolts are allowed to be run loose, the hub is toast. You don't need to lock tight the bolts to keep them tight on a good hub.

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