Advice/Warnings - Changing Fork springs & oil

Any advice/warnings/special tools that I need to be aware of before I dive into my forks? The only thing I can tell from the manual is that there is a tool required to hold the dampener rod - what have you used? What about the base valve?



The only special items was a spanner type wrench (thinner), to remove the fork cap from the internal rod.

I didn't have a metric spanners. But I think a 13/16" worked.

No special tools needed for doing springs and oil.

Don't even need a thinner spanner.. just pull the spring down a bit and slip the 17mm in.



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Matt Porritt

99 YZ400F

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You dont need to pull the valves out to do springs and oil. Matt is right about the 17 mm. Simple job just dont overfill.



These guys are right, if all you're doing is simply replacing the oil then a pair of 17mm wrenches will do. Make sure to have the rebound valve screw back out all the way and also make sure that the inside of the cap meets all the way with the top of the compression rod before applying the lock nut. And don't ever grap the rod with pliers. Use two jam nuts if you need to hold it for any reasons. And don't use any solvent unless you have the means of completely removing it.

If you want to remove the damping/compression rod assembly, then you'll need to remove the base valve. About the only tool for this job is an impact gun and a 14mm allen socket, (you can now buy these on0line via Snap-On).

If you plan on taking the entire fork apart, let me know and I'll provide you with some tips.

Hope this helps.


Correction - one 19mm and one 17mm wrench.

Sorry about that.

I need to install the heavier rate springs, I figured I'd change the fork oil while I was in there. I don't have any intention of pulling the base valve if I don't have to.

I'm a little confused at this point. I pull the fork cap and the springs come with it, correct? To remove the spring(s) from the damper rod assy requires the compressing the spring and removing the jam nut on the bottom side of the fork cap, correct or incorrect?

thanks again,



I recently put in the big guy spring myself.

You are correct, the spring is attacted to the cap. I used a bicycle pedal wrench (about an eighth inch thick) to undo the nut under the cap. It slips right in without having to mess with the spring.

After you dump the oil and pump the remainder out with the rod it takes a while to refill properly. You will need the forks off the bike to change the oil completly.

Fill them all the way up while they are fully compressed then pump the cartrige slowly and not to far and this will fill the catrtrige with oil. This is very slow and took me 15 min per leg to get the right level. Have fun doing this I made a complete mess and filled one shoe with fork oil in the process. Don't be fooled into thinking its all out of there cause its probably not.


Here's what you want to do.

Back out the rebound screw.

Loosen the cap (1/4 turn) on top of the fork using a 19mm. It's best to do this when the fork is still on the bike.

Then remove the forks.

Then fully loosend the cap. It will lift out with the spring attached to it.

The cap is screwed onto the top of the compression rod and locked in place with a 17mm jam nut. You'll need to pull down the spring (this can be done by hand) and wedge in the 17mm wrench onto the jam nut. Then with the 17mm in one hand, and a 19mm on the top of the cap with the other hand, you can break the two apart.

By the time the cap comes lose from the compression rod, there will no longer be a load on the spring, (ie, it won't fly apart).

Remove the spring, then the jam nut, then the plastic collar.

With the fork up side down, move the compression rod in and out until all the oil is bled out (until there is no more resistance).

Then turn the fork right side up and fill up with oil, working the compression rod in and out until you have full resistance.

Then set oil height.

Slide on spring, collar, and jam nut. Screw jam nut all the way down.

Screw on cap until it makes full contact with the top edge of the compression rod. Then screw up the jam nut to lock the cap in place.

Screw the cap back on, replace fork in bike, and torque cap to spec.

Hope that helps.

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