Fork oil change

Have never changed the fork oil before and have a few questions: 1) I was planning to switch to ATF as many people have. If I do this, is there a problem with the existing oil mixing with the ATF. I will drain the old oil and clean, but do I have to be worried if I don't get all the old oil out of the nooks, etc. 2) I have read about the need to keep everything clean. Is there a special cleaning cloth people use? Do I need to worry about lint being left behind? 3) Is there a special cleaner I should use? Is PJ1 okay? Thanks in advance for you answers!

in order to make sure most all the oil& contaminants are expelled, remove the compression valving at the bottom of the fork leg - I believe this is a 22mm allen head socket. I use contact cleaner or equiv. to clean. I personally like Silkolene 5 weight fork oil, but this is a touchy subject as you will see as well as folk oil height.......another tip:

loosen fork caps before removing forks from triple clamps. You will not have to use a vise (ouch) if you try this. You may want to swap oil seals also since forks are off of bike. Hope this helps

It's 14mm hex, and yes, it's a great way to quickly get the oil out. You'll need an impact gun as well.

And I'm not sure what to say about ATF. Forks need an oil that address both hydraulic and friction concerns in a low heat environment.

Transmissions are different. Seems like a viable old school technique that could work well, but put some real research into before you cut corners.

As for cleaning, some solvents leave residues that are impossible to wipe off. Other solvents attract moisture because they cool the metal. All solvents get trapped into areas you won't be able to clear out unless you do a complete disassembly- like the valves and compression tube assemblies.

I would recommend that you just wipe stuff down with a clean rag and air blow any dust or lint.


I'm not sure about regular ATF but Mobil 1 ATF is in my forks and I noticed an improvement in the stroke after the change. I haven't heard anything negative about it either. Jeremy Wilkey at MX-Tech is the one who recommends it, and serviced my forks.

I put Mobil 1 ATF in my 01' 426 and it is great! The weight is 7.5w so it is stiffer for you faster guys or heavier riders! Im only 150 lbs and ride 99% MX/SX so it works great to stiffen up the front end when hitting big jumps and whoops! Very noticable difference!



I get my kicks on a 2001' YZ426!

Friendswood, TX


Have you noticed the need to change your oil any sooner than usual? The guy behind the counter at the local Yamaha shop said that you would need to change your fork oil more often if you used ATF. Not sure why. Shaun and I talked about this and figured that ATF would break down much faster in a transmission application than a fork application so could not understand why this might be the case.

I have about 3 months on my ATF and love it! I wouldn't see why it would break down quicker, if anything it would last longer! It also is about 1/2 the price of Suspension fluids (so even if it did break down quicker it is cheap anyway)! If you are trying to decide to put it in or not...I would give it a try, im sure you will like the results!

There is also one other thing that I have noticed...When I had the stock oil in the forks the seals would leak every 2 rides (even when the bike was brand new and the stock oil wasnt broken down yet). And now with the ATF it hasnt leaked since I put in in there (about 3 months ago)! Maybe the ATF isnt as hard on the seals, I dont know...but it works! Hope this helps,



I get my kicks on a 2001' YZ426!

Friendswood, TX

[This message has been edited by motoman393 (edited 05-16-2001).]

I do know that there is an additive in ATF that causes seals to swell. Manufactures spec this.

Perhaps that's why your leak went away.

Is there still a difference in ATF fluids between Ford and GM types. I think they used to call it Dextron and something else.

The other debate is the issue of viscosity. Most will say never go over 5wt. Some say a single weight is the way to go. I'm not sure what ATF is.

Fox once put on a suspension design seminar and the man himself said that water is the perfect viscosity (of course, not implying to use water). Redline also makes suspension oil called "Like Water" for people of this religion.

I have never tried either product, (ATF or the Redline) so I'm not making any recommendations. Just chatting.


Hey JBM, how often do you need to change the ATF? What does mx-tech recommend?

For some reason, I keep hearing about Mobil 1 ATF. What is so special about it? It looks like mx-tech is using it. What about the others? I would think that if it is that good, everyone would be using it. It is interesting that the ATF has a seal swelling agent. I would think that this would increase the dampening. Do you have an increase in sticktion(?).


You've probably already seen this but this is their recommendations.

"The dampening of suspension changes as the components are used. This is caused by wear and oil viscosity breakdown. It is important that your suspension has regular maintenance by MX-TECH. Improper assembly or inadequate fluids will drastically alter the way these components were designed to perform.

For the shock, we recommend that the linkage be cleaned and greased once a month. The shock's oil should be changed every 3-6 months. Seals will generally last a season, so once a year we recommend replacing them.

For the forks, we recommend that you bleed off the gas pressure once a week. Oil should be changed once a month. A complete service is suggested every 3 months. Seals will usually last 3 months, if they are not contaminated with dirt and water. Don't wash anywhere around your seals with power washer (including the chrome.) Also we do not recommend removing dust scrapper for internal cleaning. This typically frees up dirt caught in the scraper, which will attack the oil seal."

For the forks, I'd say twice a year would suffice for the casual trail rider. And for the shock probably once a year. Of course if you follow MX Tech's recommendations, it can only help.


I think the only advantage is cost. I'm not for or against it, I just think it needs some further thought.

And I don't think the seal swell adative would cause any problems. It's not optimal, but I'm sure it's fine.

By the way, it's "damping", not "dampening".


gee if it's ok to run atf in my forks i think i'll try running wd40 in place of engine oil in my motor or maby 90w gear oil in my rear shock

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