2014 yz450f fork/shock oil change help.

Yamaha YZ450F 2014

40 replies to this topic
  • yzUSMCf

Posted January 19, 2015 - 11:51 AM

#1

So I would like to change the suspension oil. I have not worked with the new kyb suspension. I don't have any experience with changing fork/shock oil. I bought the tusk fork tools to take the damper assy. And inner assy apart. So all I have to do is undo the cap pour the oil out .refill to the manual specs. and do the same to the dampner? And as far as the shock goes the manual pretty much says take it to the dealer because of the nitrogen charge. They show how to take the shock off the bike and that's it. What type of oil ? How to change it? How to charge the nitrogin and what psi?

If there is a thread or video that would be awsome ,thanks guys.

  • GHILL28

Posted January 19, 2015 - 02:43 PM

#2

There are some youtube videos of it.  

 

They are the same as any KYB stuff dating back to '05.  The shocks have been the same since....forever basically.  

 

Short version is: Overfill the fork damper, then do a full cycle to burp excess.  Dump specified amount into the outer leg.  Be mindful of assembling the jam nut/footnut so the footnut is bottomed on the rod, or your rebound range will be off.  The shock basically gets topped off through the compression adjuster, then take to a shop to hit it with 150psi nitrogen.  If you feel/hear any crackling noise from the dampers, you have air in them, so just repeat the last couple of steps in whatever video you find to correct it.



  • grayracer513

Posted January 19, 2015 - 09:24 PM

#3

Read: http://www.thumperta...-2#entry7613090

 

and: http://www.thumperta...k/#entry6860151



  • yzUSMCf

Posted January 19, 2015 - 09:51 PM

#4

Thanks for those links. Looks like I've got alot of Reading to do. Seems real complicated to change the fork oil. Like alot can go wrong. Wish there was a thorough video on the process.

  • grayracer513

Posted January 20, 2015 - 05:57 AM

#5

Simpler than it seems.

  • yzUSMCf

Posted January 20, 2015 - 07:09 AM

#6

Do I use the same oil in the shock ,inner and outer chambers of the fork?

  • grayracer513

Posted January 20, 2015 - 07:20 AM

#7

You can, yes.  But shock oil needs to be less than 5 wt.  Another thing that can be done is to use a light oil like a 2.5-3 wt in the fork cartridge, and a heavier, 5-7 wt oil in the outer chamber.  The outer chamber controls no damping, but does manage bottoming hydraulically.  The heavier oil will resist bottoming in the oil locks better, which allows you to run a lower level (I run 320-325cc instead of the prescribed 350cc).  Lowering the oil level reduces the "air spring" effect within the fork, making it plusher from mid stroke down.



  • yzUSMCf

Posted January 20, 2015 - 07:27 AM

#8

Ok cool. I'll give that a shot I'll use the s1 for the inner chamber and a 5 wt in the outer with a 325 oil level and see how it works. I don't plan on removing the dampner assy out of the fork tube just unscrewing it so I can pour and refill the outer chamber.. I don't want te deal with messing up the jam nut deal (one step at a time lol) this suspension is amazing in stock form for me at my skill level it's hard to think it could get better.

  • grayracer513

Posted January 20, 2015 - 07:35 AM

#9

The jam nut deal is simple, and you're going to be dealing with it anyway.  The main thing is that the clickers need to be backed all the way off, and the adjuster needs screw down onto the rod and bottom out on it without the nut coming into contact with the adjuster.  Then you run the nut back up against the adjuster and tighten it.

 

The mistake usually made is that guys get the idea from the manual text that the nut should be left with clearance between it and the adjuster, and then they assemble it like that.  Without the lock nut locking anything, the rods can unscrew, and then things go to shit in a hurry.



  • yzUSMCf

Posted January 20, 2015 - 08:14 AM

#10

One last question do the clickers need to be backed out all the way prior to disassembly or just when I'm putting it back together?

if I run into any issues I'll post it up I appreciate the help!

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  • GHILL28

Posted January 20, 2015 - 08:17 AM

#11

In the fork they generally don't need to be backed out.  At least I've never run into any issues with having them NOT backed out or noticed a difference in assembly and bleeding.

 

Now on the shock, you will make your life 10x easier by backing out the rebound adjuster all the way and bouncing on the shock a few times and making sure it's at full fast.  Do this before you remove the spring and the nitrogen charge.  Having that port clear and the needle backed up makes it WAY easier to bleed later on.



  • yzUSMCf

Posted January 20, 2015 - 08:39 AM

#12

In the manual it says to back them out or else you won't get the same settings once you assemble the forks.

  • grayracer513

Posted January 20, 2015 - 09:38 AM

#13

One last question do the clickers need to be backed out all the way prior to disassembly or just when I'm putting it back together?

 

Yes, they do.  The reason is that doing so ensures that the rebound adjuster assembly will screw all the way down against the rod end.  The clickers screw in against the long, hollow push rods, which in turn bear against a spring loaded needle valve inside the top of the rod, within the valve assembly to control the amount of oil bypassing the valve, and thus adjust the valve's effect.  If the clickers are left turned in part way, it's very likely that the adjuster would stop against the spring pressure before it bottomed, which would put it in a different positon than it was before disassembly.  That could make "10 clicks out" something more like 15 out, and might make it impossible to access a true setting of 3 or 4 or 5 out. 

 

So yes, it's actually quite important that they be backed out all the way prior to reassembling. 



  • yzUSMCf

Posted January 20, 2015 - 10:04 AM

#14

Cool

  • GHILL28

Posted January 20, 2015 - 02:38 PM

#15

Wouldn't that only occur if the rebound adjuster were turned in ALL the way?  Or turned in past all the way once it was removed from the rod?

 

If it's still in the middle of it's range somewhere, it'll still come back to the same spot and not bottom against that.  Unless I'm missing something.



  • grayracer513

Posted January 20, 2015 - 04:02 PM

#16

Wouldn't that only occur if the rebound adjuster were turned in ALL the way?  Or turned in past all the way once it was removed from the rod?

 

If it's still in the middle of it's range somewhere, it'll still come back to the same spot and not bottom against that.  Unless I'm missing something.

 

It may or may not, but it's easily avoided by backing them out.



  • yzUSMCf

Posted January 21, 2015 - 12:25 PM

#17

What is the psi of the shock nitrogen charge supposed to be at?

  • grayracer513

Posted January 21, 2015 - 09:25 PM

#18

Opinions vary. 140-175 pretty much covers everybody, though.  I like 145-150. 

 

When you open the shock, do so carefully, as there is almost absolutely always a significant amount of accumulated gas pressure trapped in with the oil.  Cover the compression adjuster with a rag, use eye protection, and hold in against the pressure to damage to the top threads as the adjuster clears them.



  • GHILL28

Posted January 21, 2015 - 09:38 PM

#19

Gray what's your method for topping off and getting the last couple air bubbles out of the shock Cadj and sealing that up?  After doing a shim shuffle on my 2014 shock tonight I was reminded why I hate working on the KYB stuff versus Showa.  I can still hear a small single "crackle" when sitting on the bike, but couldn't feel or hear any air in the shock when cycling by hand.



  • grayracer513

Posted January 22, 2015 - 07:33 AM

#20

It's a bit of a PITA, isn't it?  I take take the Comp adjuster apart by using the LS screw slot to turn the HS nut/LS screw assembly down out of the adjuster housing.  With the shock filled and bled internally, stack the adjuster core on top of the exchange piston shaft.  That takes up almost all of the available space, and if you then fill the adjuster chamber as full as you can get it, there's very little room for any air.  When you then screw the adjuster housing down onto the adjuster (as you simultaneously screw the adjuster back into the housing), the housing displaces pretty much all of the remaining air out.

 

Something that you have to watch out for is that you have the shock horizontal enough to keep the adjuster cavity filled, but at the same time, upright enough to let all the air out of the reservoir chamber.

 

One of these days, I'm going to start putting bleeder screws in them.  There's a boss for one right under the top shock eye.







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