Nitrogen bladder burst

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#1
Hi,
A month ago when I was completely ignorant about the suspension on my '90 YZ125, I filled the nitrogen bladder with compressed air, thinking it would make my rear shock stiffer. I realized my mistake a day later and went to let pressure out through the schreader valve, only to have oil squirt out. I was told my nitrogen
bladder burst.
Also, slowly, shock oil has been leaking past the seal on the end of the shock body down the shaft and off the linkage on to the ground. After about 3 weeks the leaking stopped, so I'm assuming all the oil leaked out. The bike has no damping, it bounces on the spring a lot. (this is a kayaba rear shock.)
I haven't touched the bike since this problem sprang up (except when I rode it for like 10 minutes a few days after this first happened) so I was wondering what exactly has to be done to the shock to get it fixed, (like just a new nitrogen bladder, or just a shock rebuild...) and if anyone knows how much it would cost.
Some dealer told me a couple hundred, another told me $150. I need to know what exactly needs to be done to get the shock fixed. Any help would be appreciated, thanks.
 
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#2
Doesn't sound good......a shock that old will certainly need a complete rebuild. The body should be re-hardcoated if it isn't worn too bad. I would expect to spend 150-200 bucks if the body is salvagable.......you should be able to get it revalved while it is apart for no extra charge. The bigger susp shops may have a good shock gathering dust!
 

Rcannon

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#4
You could also order parts from Jeremy's site and rebuild the shock yourself. I did the shock on my YZ 250 last year and it was not too difficult. I needed less tools to deal with my shock than I did my front forks. http://www.mx-tech.com/core.asp

Try the site, go to downloads, and read through the instructions yourself.
 
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#5
I hesitate to rec people try to rebuild their own shock on something as old as his bike. If you have no experience in how they work or what to look for you can throw money at it all day and still have nothing. I would be very surprised if the body on his shock isn't damaged.....if you don't know what to look for or how to measure it, new parts (seals/bushings) aren't gonna fix it.

JMHO!
 

Rcannon

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#6
KTM lew, your point is well taken.

Here comes the stupid question...Do the shock bodies wear out or get damaged from running wil low/no oil in them?
 
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#7
Originally posted by Rcannon

Here comes the stupid question...Do the shock bodies wear out or get damaged from running wil low/no oil in them? [/B]
Both......lack of oil changes/service create floating debris that work as a hone on the surfaces, the piston ring wears out, the shaft is no longer centered so the seal leaks.....no oil.....ouch!

Actually the KX shocks were the worst for this.......but any shock that is run dry will be damaged to some degree. :eek:
 
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#8
Im positive theres still oil in it. I just checked and there is still oil on the linkage that came off the shaft. It compresses/rebounds fine, no binding or squeaking or anything. Given this information, how good are my chances for a salvageable body? Thanks.
 
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#9
JH53210

There is no way to know if it is damaged without taking it apart. You might be OK......it has to come apart......it's no good as is, right?
 
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#10
I have a good idea about the a shock, with the shims, piston, valves... but I've never taken one apart. I dont know if its no good or not, but what I'm thinking is if I could take apart the shock and just check for piston and ring damage, and if there isn't any damage to the internal parts or body than I could just replace the bladder?
 
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#11
JH......Yes!

If you feel comfortable working on it then download the instructions from MX-Tech and have at it. If you have a local machine shop that does hydraulic cyl repairs, they should be able to measure the body for excessive wear or scoring. I would at least replace the seal/sealhead and piston ring, along with the bladder.

Good Luck!
 

kevin5758

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#12
Something that old with a leaking seal could have a bad shaft. Check the shaft for an oblong discoloration toward the middle, or more obviously, pitting. If the body is worn, you can see it. To double check, clean it out and run the piston up and down in the body. If will feel tight at the top and feel loose in the middle if it is worn.
 
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#13
Kevin......excellant point on the shaft.....I hadn't thought of that.

I still think I would keep an eye on ebay for a spare.
 
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#14
Thanks for the input, just one question: what is pitting?
Looking at the shock on the bike, the shaft is chrome and towards the middle the chrome color isn't as shiny, but barely noticeable. The seal started leaking due to me filling the bladder with too much pressure, so I'm pretty sure the shaft isn't bent/damaged.