Pics of busted chaincase...

Budweiser

Budweiser

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Joined
Feb 26, 2005
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63
Age
53
Location
Central NY
2000 SXR 700 with 8600 miles. I think the sheared bolt in the last pic caused this... What would cause the bolt to shear? Anything else I should take a look at before rebuilding? Bearings all look good and were replaced at around 4500 miles.

Thanks for replies!!!
 

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I have chain and gears if you need them.


Look on ebay for chain case. They are everywhere.

Things that cause this......

1 Excessively worn chain, too loose chain slopping around

2 over tight chain( got too much stress and blew apart)

3 bad speedo bearing cause alot of slop in the shaft and explode the chain case

4 inporper gears. hyvo and non hyvo chain and gears mixed together.
 
Check Jack shaft bearing!

Did you check your jack shaft bearing on the secondary side? Is that the chain adjustor bolt that was sheared off? I had to replace the jackshaft on my 03 viper at 6000 miles, since the bearing was shot and wrecked the spline end of the shaft, secondary side. Did you keep your chain adjustor bolt tight enough? I would use all new OEM bearings, since you already have it apart, why take a chance with used ones. I find the bearings life to be about 6000 miles on average or about 4 years.
 
My 2002 SRX did the same thing last year. The bolt head just popped off. I welded mine back together and bought new chain and gears.
 
i just ordered all new gears, chains and some misc. parts that were ruined. $143.08 The bolt that broke is the bolt that holds the larger drive gear on...I think. It was bolted into the drive shaft.

I'll check the speedo bearing tomorrow. I don't really want to replace the 2 bearings on the chaincase as they are $45.00 a piece. They seem fine. This is my secondary sled that my brother rides and he's paying for everything.

Chain adjuster was tight enough. I finger tightened it and then backed it off a 1/4 turn. Oil was changed prior to riding. Rode the sled over 170 miles after that with no issues.

Chain could have been excessivly worn, 8600 miles. Again, this is my second sled!

I have a bid on Ebay right now and if I don't get it I can get it from someone on this site...hopefully!

Thanks for suggestions and keep them coming!!!
 
It looks like to me the bolt broke first. Likely due to having been overtorqued at some point previously. I am guessing that the rest of the damage is a result of the bottom sprocket coming in contact with the cover (along with the chain). At some point it cracked the cover, and then a broken link in the chain caught this crack and opened things up abit.

You should post on www.SnoWest.com and ask if this is a good example of a ported chaincase. Be sure to ask how many horsepower it should add.
 
The bearings in the chain case I believe are just 6205 bearings. They are cheap. Get NTN for around $8- $10 CDN. Seems like a good bearing to me. It was a NSK bearing that came out which is made by NTN.
 
It could have been a defective bolt - especially seeing that the same thing happened with one in the other post. I have seen that problem happen before and be the cause of replacement programs. If it would be from incorrect metallurgy or caused by the forming process I do not know. The bolt head likely either got between the chain and sprocket or between the chain and case at the sprocket and broke the case open.
As a preventive measure, I think that I will replace that bolt on my sled the next time I have the case open.
 
PZ 1 said:
It could have been a defective bolt - especially seeing that the same thing happened with one in the other post. I have seen that problem happen before and be the cause of replacement programs. If it would be from incorrect metallurgy or caused by the forming process I do not know. The bolt head likely either got between the chain and sprocket or between the chain and case at the sprocket and broke the case open.
As a preventive measure, I think that I will replace that bolt on my sled the next time I have the case open.
Click to expand...


When I looked up this bolt and ordered it, it did have a replacement:

BOLT,FLANGE (3GD)
95817-10025-00 (replaces 90105-10751-00)
 
I would also recommend using a torque wrench set to the proper torque. The torque for that bolt that holds the driven gear on is 35 ft. lbs.
 
Last edited:
http://www.totallyamaha.net/forums/search.php?searchid=587801. This is the post from last season. What I think happened was overnight, after a ride it dipped to -25F. The lube and maybe some water froze in the case. When I moved the sled forward the ice around the bolt loosened the bolt just enough to give it some play. Then in the woods the constant load back and forth finally broke the head off. Realistically, that bolt is the only mechanical means to hold the drive shaft from moving back and fourth. There is quite a load on it, laterally.
 
When i pulled my chaincase this summer the same bolt was sheared off just as you speak of. Guess i got lucky cause it didnt do any damage!
 
Replace the bearings

The chaincase bearings are 6205's as mentioned above. They are less than $10 each! REPLACE THEM!

Madmatt
 
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