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Compression chamber oil '06 forks

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I have been watching videos on how to rebuild dual chamber forks while waiting for tools, and parts.. I have never worked on yz forks before, but everything looks straight forward.

 

One part is unclear though, after filling the chamber with oil, pumping that rod slowly till all the air is out. Then, installing the valve, screwing the top back together.... is there a certain amount of oil that is supposed to stay in there? Or does it all have to be pumped out of those two holes?

Edited by Fasz Kalap

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You will fill the inner chamber with oil before dropping the compression valve assembly in, and only fill it to an inch or so below the bleed holes or else you'll just waste more than you need to since the level will rise up and the extra will drain out when you drop the valve in and work it down. I fill it with the damper rod completely extended. When you first fill it, tap the sides with a screw driver handle or something while you hold it at an angle and sort of roll it around to get all the bubbles out from every angle. Air bubbles have lots to get trapped in inside there, so be diligent. Then work the damper rod a few times to distribute the oil into the valving, then tap and roll a bit more. You want all bubbles out. If the oil level goes down during this, fill it back up to a little below the bleed holes before the next step. Keep working it until you don't see any bubbles coming up for awhile.

Then when it's time to install the compression valve, first drop it in and let it sit on top of the oil and work it in with some positive pressure from the top while turning it a bit left and right. Tilt and roll the assembly while you do this to get more and newly trapped bubbles out. I then clamp the inner chamber body gently in some aluminum jaw covers for my vice and have a garbage can positioned underneath to catch the excess oil. Work the comp valve down in there until you can just get it threaded by hand - you'll probably need to push the damper rod up a couple inches and pull it back out while pressing firmly with the palm of your hand from the top, while twisting right trying to get it to catch a thread. Don't push the damper rod in too much though and allow the comp valve to seat with more rod still to extend - you want just the right amount to where it takes some force from the top while twisting to start the threads with the damper rod all the way out. It may take more than one try your first time. Just refill it and do over.

Then when you've got the threads started, tighten it up with the compression valve tool/fork cap wrench. Now for the most important part (aside from making sure you got all the bubbles out before you installed the compression valve): bleeding the inner chamber. I use a shop towel or something and hold the assembly with the towel around the top by the two bleed holes. All the towel is doing is blocking and absorbing oil that shoots out of the bleed holes. Holding the assembly perpendicular to the floor, hold it over the garbage can and slowly push the damper rod all the way in until it stops and hold it there. You'll hear and see all kinds of air and oil come shooting out. Let it spring back out and then do that a couple more times. After a few bleeding iterations, it shouldn't be pushing anything (or much at all) out of the holes.

You know you've done this correctly if you can push the damper rod all the way in and it pushes back out and stops with around 10-50mm to go. I read that range somewhere else one time, honestly - 50mm seems like too much to me and I usually get it to within about 10-20mm. Then if you pull it the rest of the way and it doesn't suck back in, you're good. If it does suck back in, you probably have some air in the system and you need to pull the comp valve back out and try again. Don't give in and put it back together as is like that because your forks won't dampen properly and they'll be mushy. On the other hand if the rod comes springing right out all the way to the stop under force, you probably need to bleed them more, even holding them at an angle while you push the damper rod in, because they have too much pressure and will feel harsh.

The other thing I do when putting the forks back together is minimize the time that they're upside down or even horizontal. A little bit of inner chamber oil will usually leak out of the bleed holes and you want to really limit that. Turn the forks so the bleed holes are level, at 3 and 9 o'clock, and that'll help. I also keep them covered with my fingers as much as possible. Otherwise have everything cleaned up and ready to go once you start reassembly so you can get it done fairly quickly.

One other tip - don't forget to install the rebound adjuster tube before you screw the adjuster back on! It can be easy to forget. I mean, not that I ever forgot it, but I had a friend who did once...

Good luck! This is way better than paying someone to do this for you - it's not difficult. Check out the Smart Performance website for more tips and instructions on this and search TBT Racing on YouTube for his video demonstration of this - those resources really helped me my first couple of times.

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RockerWR450,thank you .that's the info I was looking for. Worked well for me just as you described is what I did .

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Just wondering if this will work? I am chasing a problem, and want to keep everthing the same.

 

Take apart bottom of fork first, then plug off bottom of forks with an expansion plug. Flip around forks, take out top part. Pull out springs, replace, and put back together without messing with oil? 

Edited by Fasz Kalap

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Just wondering if this will work? I am chasing a problem, and want to keep everthing the same.

 

Take apart bottom of fork first, then plug off bottom of forks with an expansion plug. Flip around forks, take out top part. Pull out springs, replace, and put back together without messing with oil? 

If your just replacing the main springs just chance that oil when you take it apart. You dont have to take the inner chamber apart you can pull the entire cartridge, ( dont remover the big allen head part with the clicker in it) and it will have something Like 350cc? of oil in it. You dont have to bleed anything to replace that oil you will just pout it in and your done. Dont quote me on that oil amount I dont remember the stock amount but Im sure someone will. If you dont have fork oil search mobil one syn atf. Some use it in place of fork oil.

Edited by nickmell

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Technically, you don't have to mess with the outer chamber oil when changing springs either.  You flip the fork over, remove the rebound adjuster and press the damper rod in a bit.  Then you replace the rebound adjuster without threading the adjuster back onto the damper rod.  Then you can flip the fork right side up, wait a little bit then pull the damper and spring out.  You'll lose a minimal amount of oil do this.  Adding a few cc back in will take care of it.

 

This is really something you do when you're making changes to valving or something repeatedly and have fresh oil already.  If you haven't changed the oil in a while or don't know when it was changed then you should do it anyway.

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Oil was dirty, so I dumped it. Both forks took about 20 minutes doing it for the first time. Saved about $175 

 

Thanks

Edited by Fasz Kalap
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