2005 yz450f fork oil change


5 replies to this topic
  • rickyz450f

Posted June 18, 2007 - 12:37 PM

#1

how hard is it to change the fork oil ,are the tools expensive

  • SC_Spode

Posted June 18, 2007 - 01:16 PM

#2

how hard is it to change the fork oil ,are the tools expensive


Inner, outer or both?

Changing either isn't difficult if you have the correct tools. You can probably get them from someone on eBay pretty reasonably priced.

The biggest headache is bleeding the air from the inner chamber. The way it's designed causes it to trap air and doesn't provide for an easy way to purge it.

:thumbsup:

  • grayracer513

Posted June 18, 2007 - 03:46 PM

#3

The biggest headache is bleeding the air from the inner chamber. The way it's designed causes it to trap air and doesn't provide for an easy way to purge it.

That's actually not the case. Bleeding air from the damper assembly is a simple matter of excluding it in the first place. The dampers are filled so that the oil is above a set point in the cartridge. The rod is then compressed, and the base valve assembly is inserted and tightened while allowing the rod to extend. When done right, no air is assembled into the cartridge, and in fact, a small amount of excess oil is included, which you force out by forcefully compressing the rod to its full extent of travel once, then draining off the excess.

The '06-7 works the same way. It could hardly be any simpler.

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  • SC_Spode

Posted June 18, 2007 - 05:43 PM

#4

That's actually not the case. Bleeding air from the damper assembly is a simple matter of excluding it in the first place. The dampers are filled so that the oil is above a set point in the cartridge. The rod is then compressed, and the base valve assembly is inserted and tightened while allowing the rod to extend. When done right, no air is assembled into the cartridge, and in fact, a small amount of excess oil is included, which you force out by forcefully compressing the rod to its full extent of travel once, then draining off the excess.

The '06-7 works the same way. It could hardly be any simpler.


Gonna have to disagree with this one.

I've spoken to Terry Hay, TT members Russ17 and shockdoc and all are of the opinion that I came to - the way the base valve fits into the assembly guarantees that it will trap air.
For those not familiar with these gentlemen, they all own their own suspension businesses.

Look at the plastic piston and where the valving rests - it forms an umbrella that holds an air pocket when inserted. You can force excess oil out but you haven't forced the air pocket down and out. Much like bleeding a front brake caliper - just because there is fluid coming out of the bleeder doesn't mean all the air is purged.
Terry in particular has gone to great lengths to solve the problem on the 05's.

There are ways to eliminate it but to say it couldn't be simpler is misleading to someone that has never attempted it before.

But don't take my word for it - he can feel free to read here, here and here.

:thumbsup:

  • grayracer513

Posted June 18, 2007 - 07:44 PM

#5

So, the '05 apparently has some issues that the '06 does not. I haven't had the opportunity to work on any of that particular fork, but I have done several '06's already, and had no trouble with them at all. However, the '05 is evidently different, and I do recall having heard something about modifications to the IC spring etc.

I saw the procedure in the manual was the same, and incorrectly concluded that the results would be the same. If nothing else, this illustrates the hazards of doing that. :thumbsup:

  • SC_Spode

Posted June 18, 2007 - 08:08 PM

#6

So, the '05 apparently has some issues that the '06 does not. I haven't had the opportunity to work on any of that particular fork, but I have done several '06's already, and had no trouble with them at all. However, the '05 is evidently different, and I do recall having heard something about modifications to the IC spring etc.

I saw the procedure in the manual was the same, and incorrectly concluded that the results would be the same. If nothing else, this illustrates the hazards of doing that. :cheers:


Yeah, the 05's are, let's see... how to say this nicely... a booger. :thumbsup:

The first time I worked on them I didn't see what all the fuss was about - until I realized that they have an air trap designed into them. :worthy:

The simplest ways I've thought of to allow the air to escape during reassembly are to turn a taper on the inner shaft that the piston seal rides on so the air can escape and then the piston can slide up into position on the full diameter section to seal... or ... machine a short vertical groove low on that shaft that serves the same purpose. But not everyone has access to the tooling to do this.

There are some bleeding tricks that are relatively succesful, but I'm never 100% sure about it.

I even played with these things in a clear tube with water to see what was going in there. :bonk:
Short of assembling them while submerged, I can't guarantee they're air-free. :lol:

Which is my next goofy project - building a simple assembly to do just that.

I'm working on valving a set right now for woods riding - we'll see how it goes.

And the 06's are the bomb. :busted: I've got 'em on my 450 and my 125. Best thing Yamaha ever did for their production suspension. :thumbsup:

:lol:





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