Fork oil replacement

I've been quasi-religious about cleaning the muck out from under my dust seals... :) ...but inevitably there's been times where oil's seeped out. Given that I've owned the bike for a few years now, it's probably more than time to check the fluid levels in the front forks and/or replace it.

Got a few questions:

1. How often do folks CHECK their fork oil levels?

2. How often (if ever) do folks CHANGE their fork oil?

3. HOW do you check the level of oil in the front forks? What are the steps? Any things to watch out for, and are their any special tools required?

4. How long does this process take?

5. What type of oil should be used? Any special brands, etc?

Sure, I might know a little about my carb, but Larry dont know Diddly about his suspension! :D

Thanks in advance amigos.


I usually change my suspension fluids, front & rear, 2 or 3 times a season. You would be amazed as to how contaminated it gets with dirt and metal filings from your suspension being broken in, especially when your bike is new. This season, I've been using RED LINE LIKE WATER synthetic suspension fluid. It comes in 5 different viscosities. I prefer the clear, Like Water grade, which is 1/3 of 5wt. Pricey, but worth it. :)

So how do I go about changing it? What are the steps? Also, how do you measure how much is in there (so I can compare the level to the spec's in the manual)?

I sort of figured that I've been a "negligent owner"...but it's time to take care of that now... :)

Please advise...


To do the job right, you need to COMPLETELY disassemble the fork, which is mucho easier than it sounds.

You will need a pneumatic air wrench, w/ the correct size allen socket (for your base valve)


a cartridge rod holding tool, along w/ normal metric wrenches.

If it has been that long, you MAY want to consider changing out your seals as well. For the time and cost of new oil, it is worth it to pop new seals in. Factory Connection offers SUPERIOR seals for our bikes. For seal replacement, a REAL seal driver works best, although guys have used PVC tubing as a seal driver.

See Garret Bergs website for some nifty ideas:

link is under Tech Articles

I've ridden about 15,000 hard, dusty miles since I got my bike in April 2000 and have changed the fork oil 5 or six times since then. It looks really nasty each time. I have a buddy with an '01 WR426 who rides with me almost every week and he hasn't changed his fork oil once, either. (He's an excellent mechanic but for some reason hasn't done any suspension maintenance yet.)

I don't have the patience to explain the whole fork oil replacement procedure but I'll try to give you some pointers.

-Don't try to short-cut any steps. Take off the handlebars.

-Get a big pan to catch the old oil and be prepared to get fork oil everywhere.

-Loosen the fork caps while the lower pinch bolts are still tight and retorque the fork caps with the lower pinch bolts tightened.

-Get a thin 17 mm open end wrench before you start the job because you'll need it. A regular 17 mm wrench is too thick to fit in between the metal cover and the spring. You could modify an existing wrench with a grinder if the tool isn't to high-quality for you to ruin.

-I made a fork oil level tool out of a large syringe, some thin (1/8") brass tubing, and a thin hose. You measure the fork oil level from the top of the fork tube while it is compressed all the way down with no spring in it.

-After you have gotten all the oil out and pumped all the air bubbles out of the inner assembly, fill the fork tube almost to the top. Then suck out the oil until it gets to the right level. An easy way to do it is to make a mark on the brass tube of the desired level (for argument's sake, 100 mm). Then put a zip tie tight on the tube at that mark. Now stick the tube into the fork tube so that the zip tie rests on the lip if the open fork tube. Then suck out the fork oil with the syringe (it would be connected to the brass tube by the hose) until you can't get any more oil out because it's sucking air. The fork oil level is now set at 100 mm.

-Read the manual because it tells you what to do.

I just drop the forks out - no need (that I am aware of) to take off the bars. Make sure when you dump the fluid that you just keep pumping the inner rod (springs removed) up and down to remove even more fluid. I would spend the $$ (if you plan of ever doing this again) on a oil height tool. They are VERY handy. I normally do not remove the base valve, but if you want it as clean as possible and also what to check it - not a bad idea. Very easy, very fast, but get the height tool. I change mine 3 to 4 times a year. Oh, and you may WANT to remove the bars and grease the steering head bearings while you have the forks out.

Thanks gents. Sure appreciate the input. Sounds like I've got some tools to go buy...

So does fork oil freeze? I think everything else does up here in MN! :) Just got back from my last day working in CA and it's freekin' 45 degrees and raining. Where did my summer go?!?!?! :D



Strick, that's what I was thinking of regarding the handlebars but I didn't say it- might as well grease the steering head bearings while you're at it. I always do them together so it's become kind of automatic for me to do it that way. And, since I torque the caps wile they're in the clamps, I have to take the bars off to get the torque wrench on the cap.

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