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Rear shock Dissasembly

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Hey guys, I have a 04 yz250 with 06 yz250f suspension, I am gonna do fork seals and shock seal because there all leaking. Can anyone explain how that shock comes apart and what do you recomind going with oem after market what brand, I know the shock dosent have oem replacements but let me know.

Thanks Joe

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for make a better job use only oem parts if you can, kyb seal or skf

kyb fork oil and shock oil if you can or other (good) oil

check on you tube more video "how change fork seal"

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I just took my shock apart last night in order to change out the oil. I followed this write up.

http://www.thumpertalk.com/topic/631120-dr-350-shock-gold-valve-install-with-pictures/

It is specific for the the DR350. But I think most shocks are mosre or less built up this way. Themain difference would be the piggy back vs the remote resivoure. But I think they are built/set up pretty much the same.

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Ive got the shock all taken apart, now im waiting for parts, I have some idea on how to rebuild but I am not certain on bleeding all the air?

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As far as bleeding the shock...I use two large zip lock bags to cover up each end of the shock (one on the top side of the shock and one on the bottom side). That way if any shock oil should erupt, it stays contained in the bags and not all over your walls (ask how I know). It also allows you to use that oil instead of it getting wasted on the ground or down the drain or whatever.

As far as shock bleeding procedure, there are quite a few around. I'll let someone else suggest their method.

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I prefer the "Race Tech" method. Way less jagging around, and the bladder isn't left fully chaffing on the bladder reservior.

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I prefer the "Race Tech" method. Way less jagging around, and the bladder isn't left fully chaffing on the bladder reservior.

I beg to differ on the first point. On the second, what makes you think the SPI method would lead to the bladder contacting the reservoir wall?

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I tried the SPI method that DaveJ posted up....that method didn't work well for me. I use a method suggested to me by theDogger, worked perfectly my first attempt without any mess. I believe the Race Tech method and the method suggested by theDogger are very similar.

With that being said, everyone has their own method of bleeding shocks. Just find a method that works for you and go with it.

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I beg to differ on the first point. On the second, what makes you think the SPI method would lead to the bladder contacting the reservoir wall?

I don't think you can move the shockshaft fast enough to open the valving, without cavitating, when the shock body is closed and the comp valve is out. There is nothing to push against, and "pulling" fast always cavitates it. So you end up moving the shaft slowly back and forth, fluid just bleeding through the bypass. When the res is closed and you work from the sealhead, the air naturally rises out of the rebound shock orfices, and pushing in fast naturally pressurizes and stabilizes the fluid, opens the compression valving, bleeds more effectively (for me). Finally, the act of setting the sealhead forces oil into the res, compresses the bladder slightly, and the bladder acts on the oil from all sides rather than mainly "extending" to act on the oil. Unless I missed something, there is no step where this takes place in the other method.

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well guys I did sucessfully tear the shock down and clean everything, but I didnt feel comfortable doing the bleeding and I did not have access to nitrogen so I took it to a local cycle shop (TRACK-N-TRAIL) and had it bled and re assesbled, needless to say have the correct fluids and non leaking shock and fork seals made all the difference in the world. I did the fork seals on my own and used the old fork seal to seat the new one, and I used an axle block lip for the inner champer(Im not about rigging) but this was a very snug fit. Thanks for the help and I appreciate it. Now Im swaping the 04 frame to a 05 alumnium frame I have the new linkage and im going to order the stator bracket and exhaust spacer, any thing I missed????

Thanks Guys

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I don't think you can move the shockshaft fast enough to open the valving, without cavitating, when the shock body is closed and the comp valve is out.

This is why I make one small change to the method. Following the basic fill and bleed with the adjuster opened, I refill as necessary and assemble the adjuster housing onto the shock. With the shock closed, I add 20-30 psi to the bladder, which allows me to pump the shock a full stroke under pressure without moving the seal head up the bore.

Nobody is ever going to be able to pump a shock manually hard enough to cavitate it in any true sense. The level of vacuum required to accomplish this is simply beyond human strength. What frequently does happen is that without the shock closed, the resistance of the compression stack will pull the seal head up in the bore suddenly, and that can cause a variety of annoying problems. Adding a little pressure avoids that.

Afterward, dump the pressure, remove the adjuster housing, and finish the assembly, filling as Dave describes. As far as the bladder goes, the design of it keeps it away from the reservoir walls if the shock is actually full when you pressurize it, at least in the KYB's. None of mine have ever shown any indication that they ever contact. The only time they would is if someone were to recharge a shock that had lost some fluid. If the bladder collapses on itself without pressure, it should really be replaced, although I have reused them by filling them with 3-5 psi to restore their shape before filling the shock.

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Gray if you pump a fork tod hard with no base valve it foams the oil terrible, is this not cavitation?

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It could be, but if it's accompanied by a slurping sound, it's more apt to result from air being drawn past the rod seal. The compression/mid valve in a fork cartridge is a great deal smaller than most shocks so it's easier for a human to create the huge pressure drop required.

Hydrodynamic cavitation is the process of vaporization, bubble generation and bubble implosion that occurs in a liquid when it either flows through a structure or an object moves through it and the pressure on it at some point is rapidly reduced to a point below its vapor pressure. In order to cause it, you have to create a area of depression behind the moving valve that is low enough to "boil" gas out of the liquid. The subsequent collapse, or implosion of the gas bubbles that form as they move away from the immediate area is what causes cavitation damage. The resistance to true cavitation really very high, and I just don't see it happening from pumping by hand. But, I could be wrong.

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Maybe cavitation is not the correct term in this case?the Mx tech vid with the wires holding the comp shims open seem a better way to get the air out than ramming it through the oil andcthen waiting for it to rise?

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Maybe cavitation is not the correct term in this case?the Mx tech vid with the wires holding the comp shims open seem a better way to get the air out than ramming it through the oil andcthen waiting for it to rise?

One of the things that we didn't touch on is the fact that when you're bleeding a damper, there's already air in the oil. Forcing these already separated bubbles through the valving at speed breaks them into smaller bubbles and foam that takes even longer to rise to the top. That's probably what the video you mentioned was showing. Don't need cavitation for that.

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Agreed that's where the vac pump comes in, trouble is they can pull air by the shaft seal

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