How Much Fork Oil is Required?

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#1
I have a 1989 KDX and Im ready to change the fork oil. I dont have a service manual and the Kawasaki dealer does not have the specs on how much fork oil is required per fork.. Does anyone know how much fork oil is required per fork? Also, How would I know if the rear shock requires an oil/nitrogen change as well? It seems to be functioning correctly..
Thanks
 
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#2
I'm not postivie but last time I changed my seals they told me about 614-625 cc of fork oil per fork.Not sure about the shock sorry.
 
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#3
Manual calls for 140mm+/-2 for oil level. (Measured from top, fully compressed and springs removed).

If the rear shock has never been serviced, it surely could use an oil change now :)
 
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#4
It should take about a quart and a half to do both forks if they are totally disassembled. And set to 100mm when compressed w/o springs.
Good Luck
 
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#5
Volume vs: level

It's already been said...but to make a specific note about it, it's NOT a matter of volume, but level. Volume would work if you knew you had not a drop of oil IN the fork when you started...but that isn't likely.

Besides, the level method is much easier.

Put in more oil than you need. Using something like a large animal syringe (available at your local grange sorta store) and a piece of tubing attached to reach 100mm into the fork (for example), draw out the excess.

With springs out, fork tube completely compressed, fork held perpendicular (90ยบ) to the ground. Yes, you have to take the boots off. Make sure you've pumped the piston rod a few times to remove any air..let them set for a bit to let the bubbles clear.

Oil of choice from j. wilkey is mobil-1 atf, btw.

While you're inside, set the preload to something useable. OEM preload is w-a-y too much. Use a piece of 1" schedule40 PVC to make a spacer to a reasonable ...say maybe 10mm?...preload.

If you happen to be using .40kg/mm springs, consider a set from a late model XR400. They're considerably longer than OEM (about 60mm longer). Moh spring is moh better than a piece of tubular steel! (imo) AND they're hot wound to boot!!

As far as WHAT the level should be...100mm is a starting point. More oil for increased firmness, less for less. NOT to be used as a substitute for proper spring rate and valving!
 
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#6
OK, a sort of related question about fork servicing. I got stiffer fork springs & a gold valve (The whole setup & valve stack was recommended by Fredette). Jeff recommended that I use 7.5 wt oil 4" from the top, which I must say made an absolute world of difference. I'm now getting ready to change the oil & service them. Only problem, the shops in my area only have Bel-Rey 7 wt. instead of 7.5 (PJ1?)as recommended by Jeff. Will a .5 weight difference in oil be noticable? Wouldn't this be able to be corrected by running 1 or 2 clicks stiffer on the damping adjustment? I know this may be a little anal, but should a KDX be treated with any less respect, especially since I spent the money & time to improve the fork action??? Thanks in advance for any input on this!
 
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#7
Well....yeah..

I know this may be a little anal...
But it is a question I've asked before....

I used to think that mixing a 50/50 of say, 5 and 10 weight oil would NOT give you a resultant 7.5 weight oil.

I was corrected by a petrochemical engineer that said that is exactly what would happen.

So, for one, mix a quart of 10W and a quart of 5W and you'll have two quarts of 7.5W.

For two, I'll bet'cha a pint of your choice of draught that you would never know the difference between 7/7.5 weight oil in your forks.

For three..jeremy wilkey's recommendation of mobil-1 would render the question moot.:)
 
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#8
> So, for one, mix a quart of 5W and a quart of 7W and you'll have two quarts of 7.5W.

canyncavr - don't you mean a quart of 10W instead of the 7W?
 
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#9
Don'tcha mean....

I mean what it says.


...even if I DID have to edit it TWICE to get it!!;)

Thanks KDXdan!
 
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#10
OK, OK -- I left myself open on that one! But I did learn something new. I had wondered about mixing proportionate amounts of 5W & 10W to get 7.5W before, but unfortunately I didn't have a petrochemical engineer at my disposal to ask. By the same token, I could mix the 7W that I already bought with a mathematically determined amount of 10W oil to make 7.5 W oil. But even I am not that anal! I'll go ahead and use the 7W, which like canyncarvr mentioned, I probably won't even be able to tell the difference (especially since I haven't been riding for about 2 months now). Thanks everyone for the info-- This forum's great!
 

canyncarvr

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#11
greenrider

...but unfortunately I didn't have a petrochemical engineer at my disposal to ask.
Neither did I.

I had posed the (evidently) ignorant (doesn't mean I didn't believe it myself!;) ) idea that mixing different viscosities didn't result in an average of the mixes. A knowledgeable petro-chem type on this site set me straight.

Gee....all the things I THINK I know............... :confused: and :( !!
 
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#12
Re: Volume vs: level

Originally posted by canyncarvr

If you happen to be using .40kg/mm springs, consider a set from a late model XR400. They're considerably longer than OEM (about 60mm longer). Moh spring is moh better than a piece of tubular steel! (imo) AND they're hot wound to boot!!
Are you suggesting substituting the XR springs for cozs 89' model non-cartridge forks? Race-tech's spec sheet lists them being about 30mm shorter than stock.

Also, this 100mm level is considerably less than the manual's 140 recommended. Again, is this the suggested setting for the 89' damper rod fork? Just wanting to clarify.
 

canyncarvr

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#13
kipmax

The original point was to use 100mm just as an example. I kinda graduated to the later style of forks by the time I was done.

You are correct. cozs bike doesn't have anything to do with mine.

Thanks for the clarification.
 
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#14
greenrider200

I have a '90 kdx, and I used 7w oil, 4" from the top as Fredette suggested. And it is a true thing of beauty.

Then again, I only weigh 160 if that matters.