Servicing 2012 Ohlins Shock?

[CDBiker220]

So I just changed the oil and fork seals on the 48mm marzocchi forks. Now I'd like to attempt servicing my shock (888 model I believe). Just want to change the oil and inspect everything. There is a local suspension shop that should be able to refill the nitrogen for a couple bucks when I'm done(correct pressure?). Is their a manual for this shock or a thread that can explain how to do it? Any special tools needed?. Ive rebuilt closed cartridge forks and rebuilt a set of old ohlins(nitrogen resivior) dual shocks on an 81 husky. So i have a little bit of experience but have never tore apart a modern shock.

[GMP]

Read this thread:

http://www.gasgasrider.org/forum/showthread.php?t=12194

Pay no attention to the separator piston height dimmensions, as these were Sachs specific. Other than that it should be the same. I've done it successfully, messy but correct. You will want to get the needle for the Ohlins, as its much easier to assemble the resevoir side and hold the piston down with compressed air than manually while inserting the shaft/seal head.

[CDBiker220]

So its harder to do without this needle...but not impossible? I assume the needle is for putting air in the resivior?

Also I imagine I have to set the oil height, similiar to the measurements there for the sachs. How would I know how much to put in.

[Jakobi]

You'll need the needle to discharge the nitrogen initially (although I imagine you could work around this quote easily). You will need it to use either air or nitrogen to pressurise and depressurise the reseviour during assembly.

[GMP]

The height dimmensions are just a referance to go by to gauge if you have a properly purged shock. Basically, you start out by filling both sides so most air is purged through the comp adjuster. Then fill resevoir to top. Insert piston without introducing air, and push to bottom of resevoir. This will purge remaining air from adjuster. At this point the piston needs to be held down, so I assemble and use compressed air. If you have an extra hand or rig up a mechanical means that would work too, but be carefull not to scratch the inside of the resevoir. Now you insert the shaft assy, seal head toward clevis. While the piston is under the oil, tap on the clevis with a rubber mallet a few times to shock the shims open and release trapped air. You will see small bubbles, stop when they stop. Slide seal head toward piston, and slowly insert into shock body. Oil should be overflowing. There should be a tiny bleed hole over the oring, this is to release trapped air under the seal head. When the bubbles stop, push the seal head in to seal the oring. At this point the separator piston will want to rise from the oil displaced by the seal head, so it has to be able to move. Push the seal head down far enough and seat the snap ring, and pull back. The amount of separator piston travel in the resevoir at this point equals the amount of oil displaced by the volume the seal head over the oring, thats it.


This makes a real mess as your always working with a full and overflowing shock body. Just think out your setup before you start, like catch trays, etc. And trust me on this, the compressed air method for holding the piston is a lot easier and safer for the resevoir. One slip with a hard tool and the resevoir sealing surface is trashed.

I heard that a well known tuner at one time used to assemble shocks in a small fish tank of oil, to avoid the air problem.

[Brian VT]

Originally Posted by GMP

I heard that a well known tuner at one time used to assemble shocks in a small fish tank of oil, to avoid the air problem.

Makes sense to me.

[Jakobi]

Originally Posted by GMP

The height dimmensions are just a referance to go by to gauge if you have a properly purged shock. Basically, you start out by filling both sides so most air is purged through the comp adjuster. Then fill resevoir to top. Insert piston without introducing air, and push to bottom of resevoir. This will purge remaining air from adjuster. At this point the piston needs to be held down, so I assemble and use compressed air. If you have an extra hand or rig up a mechanical means that would work too, but be carefull not to scratch the inside of the resevoir. Now you insert the shaft assy, seal head toward clevis. While the piston is under the oil, tap on the clevis with a rubber mallet a few times to shock the shims open and release trapped air. You will see small bubbles, stop when they stop. Slide seal head toward piston, and slowly insert into shock body. Oil should be overflowing. There should be a tiny bleed hole over the oring, this is to release trapped air under the seal head. When the bubbles stop, push the seal head in to seal the oring. At this point the separator piston will want to rise from the oil displaced by the seal head, so it has to be able to move. Push the seal head down far enough and seat the snap ring, and pull back. The amount of separator piston travel in the resevoir at this point equals the amount of oil displaced by the volume the seal head over the oring, thats it.


This makes a real mess as your always working with a full and overflowing shock body. Just think out your setup before you start, like catch trays, etc. And trust me on this, the compressed air method for holding the piston is a lot easier and safer for the resevoir. One slip with a hard tool and the resevoir sealing surface is trashed.

I heard that a well known tuner at one time used to assemble shocks in a small fish tank of oil, to avoid the air problem.

Basically the same as described in the race tech bible, and also the same for shocks with bladders. Oil in res, install bladder, Over inflate the bladder, fill the shock body 3/4s. Bleed the shim stack. Fill the shock to the top. Insert the seal head as you released pressure from the bladder. Insert the retaining clip and then pressurise the bladder again.

I'm still planning on investing in a vacuum bleeder. Makes the whole process much cleaner.

[CDBiker220]

I'm gonna just have to dive into it, its a bit hard to comprehend without taking it apart first. I was just looking at the shock earlier and noticed a screw on the top of the shock body, do you use that as a bleed port? or do you just unscrew the compression screw to bleed it? I guess ill just figure it out...I've jumped into many many projects I didnt quite understand before I got it apart and I've yet to completely fail(sometimes you learn a few lessons before success though)

[STM Suspension]

Just a couple thoughts to keep you guys from killing yourselves...

You NEED a hypodermic needle to let the nitrogen out BEFORE you try to do ANYTHING else (ok, well, make sure you back the rebound adjuster all the way out before you let the nitrogen out.) There is a torx T20 screw in the middle of the cap on the end of the reservoir. That's the one. When you open it, nothing will happen. Stick the needle in there to release the pressure. Then you can safely take the shock apart. I usually use a 3/4" long 20 gauge needle. These are most easily available from your veterinarian or local farm and ranch store. DO NOT TAKE OUT THE SCREW THAT HAS THE TORX T25 HEAD THAT'S BETWEEN THE SHOCK BODY AND RESERVOIR UNTIL THE PRESSURE HAS BEEN REMOVED.

After that, it really comes apart pretty easy. The relevant thread pitches are 5x0.8 and 6x1. It's easier to use them than not. I use a little flat blade screw driver that I bent close to the tip and ground and polished until it was the shape I wanted.

10 bar is plenty- about 140-150 psi.

And yeah, vacuum bleeder is so much easier. I build shocks dry. No mess.

[GMP]

Wow sorry guys, forgot to mention that about relieving the pressure first. I doubt you would be able to get at the snap ring anyway with it charged.