YZ450F fork seal and oil replacement


10 replies to this topic
  • ericus

Posted August 26, 2014 - 02:50 PM

#1

Hey all,

I have a leaky fork seal that I'm going to replace, and I thought it was a good idea to replace both fork seals while I'm at it.

Just ordered the necessary parts and tools, and this video shows how to do it pretty well:

 

That's for and '08, mine is '06. The procedure will be pretty much the same I guess? My question is, how do I bleed and replace the oil in the other part of the fork? He mentions at around 14:30 in that he doesn't bleed that part: http://youtu.be/eru0iV8sU8Y?t=14m30s because the bike has low hours.

I would like to clean out both forks and replace the oil in both of them. Any good videos or so on how to do that?



  • grayracer513

Posted August 27, 2014 - 06:54 AM

#2

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

 

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



  • ericus

Posted August 30, 2014 - 05:46 AM

#3

I think I did something wrong.. followed the video, poured new oil in (didnt open up the inner chamber) and put everything back together. I can clearly hear the oil running up and down in the fork when I turn it upside down, I suppose it's not meant to be like that?


Edited by ericus, August 30, 2014 - 05:47 AM.


  • ericus

Posted August 30, 2014 - 10:22 AM

#4

And if I open up the bleed screw on top, no air comes out, unless I compress the fork. What is wrong?

EDIT: Oh, and another thing. While taking it apart and counting the clicks on the top compression, I could turn it how many turns as possible without using force, it would never go to bottom. But it clicked all the time while turning it down/out.


Edited by ericus, August 30, 2014 - 10:24 AM.


  • Spud786

Posted August 31, 2014 - 11:25 AM

#5

Do you not have to pump the twin chambers?   why did the guy not place oil in the inner chamber.  Ive done many upside down forks, but haven't dealt with twin chambers, but I question this guy in the vid, I guess you need the Book.



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  • ericus

Posted August 31, 2014 - 01:04 PM

#6

Do you not have to pump the twin chambers?   why did the guy not place oil in the inner chamber.  Ive done many upside down forks, but haven't dealt with twin chambers, but I question this guy in the vid, I guess you need the Book.

I don't know. I have the manual, I will redo the whole thing by the books as soon as I can find a fork wrench tool for rent to open up the inside chamber as well.

 

But still, why doesn't the upper compression screw bottom in or out? There must be something wrong with that.


Edited by ericus, August 31, 2014 - 01:13 PM.


  • mch

Posted August 31, 2014 - 01:50 PM

#7

Still trying to figure out this post.  It doesn't sound like you did anything wrong from what I have read.  Since you have your forks back together, I wouldn't worry about doing the twin chamber portion until you are ready to change the oil again.. wait 6 months or so.

 

The oil you put in the open chamber is just for lubrication, the dampening parts are all in the twin chamber portion (they don't share the same oil).  If you turn the forks upside down, you will hear that oil move within the fork.

 

I don't understand what you are talking about regarding the compression screw.  The screw should stop at some point (I think it has around 24 clicks).

 

No air needs to come out from the bleed screw.  When you ride, it will build up pressure and that screw simply releases the pressure.  Just working on your forks, you shouldn't hear gas releasing when you open it back up.



  • ericus

Posted August 31, 2014 - 03:42 PM

#8

Double post, sorry.


Edited by ericus, August 31, 2014 - 03:45 PM.


  • ericus

Posted August 31, 2014 - 03:44 PM

#9

Still trying to figure out this post.  It doesn't sound like you did anything wrong from what I have read.  Since you have your forks back together, I wouldn't worry about doing the twin chamber portion until you are ready to change the oil again.. wait 6 months or so.

 

The oil you put in the open chamber is just for lubrication, the dampening parts are all in the twin chamber portion (they don't share the same oil).  If you turn the forks upside down, you will hear that oil move within the fork.

 

I don't understand what you are talking about regarding the compression screw.  The screw should stop at some point (I think it has around 24 clicks).

 

No air needs to come out from the bleed screw.  When you ride, it will build up pressure and that screw simply releases the pressure.  Just working on your forks, you shouldn't hear gas releasing when you open it back up.

 

 

English is not my first language, that might be why. I'm not that familiar with all english words for MX-parts.

On my other fork leg that I've not yet worked on, I can't hear any oil running around while turning it upside down. Only on the new reassembled forkleg. When I took apart the fork, I opened up the air bleeder on top (that bleeds the outer chamber, right?), and with the fork leg in pieces I pushed out oil from this on the right hand side of the picture: https://dl.dropboxus...29 18.56.52.jpg out of those two holes. Is that still oil that belongs to the outer chamber or did I drain the inner chamber by mistake by doing that?

 

And about the compression screw, I turned it at least 15-20 turns in from where it was, it would not stop clicking and I did not use force to turn it in.


Edited by ericus, August 31, 2014 - 03:47 PM.


  • mch

Posted August 31, 2014 - 04:06 PM

#10

The bleeder screws should have stayed in.  How much oil came out of there?  That oil is for the inner chamber and I'm guessing if a little comes out, it's not the end of the world.  I had some leaky push button type bleeders that leaked a little.  I'm not sure if pouring oil into the bleeder holes is good, because I'm not sure it will actually make it into the part of the chamber where it goes.  I assume it would, but not 100% sure and if too much went into the portion above the piston assembly, I suppose it could cause a lot of pressure.

 

As far as not hearing any oil in the other fork, I'm guessing it has leaked out.  Make sure you get some oil into it, and the seals should also be changed.. because oil doesn't evaporate.

 

I would recommend you do both forks completely, to include changing the oil in the twin chamber portion.  Also, you want to inspect for damage.  I had my 07 YZ450F taken apart in May, and I found the plastic pistons had broke.

 

Check this thread: http://www.thumperta...ce-front-forks/


Edited by mch, August 31, 2014 - 04:11 PM.


  • Spud786

Posted August 31, 2014 - 04:41 PM

#11

I went back through the video, and it mentioned , he skipped the step of bleeding the inner chamber, yet he drained oil out of it. That doesn't seem right or idea to me.

 

As far as the op, if his clickers don't bottom out, I'd say he didn't fully bottom the rebound adjuster when installing(screw it in all the way) showing that gap as mentioned in the vid, assuming nothing is actually broke.







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