Fork Seals How To Change

I did a serach on how to but nothing showed up. If any one could tell me how to do it that would be great. I have a 2002 Yz250f. :thumbsup:

Goto the motoman 393 site, and download the YZ426 manual, it has steps, manual, how to make your own tools and stuff....

Thanks for the help


Here are some intructions that I used and they are very good. I would recommend a real fork seal driver. These came from somewhere on this site a while back, but I don't remember where. I just saved them. It isn't very difficult. Just keep things clean. I didn't try the last part about the pressure relief valve and I used Yamaha suspension 01 oil,but everything I did worked out just as advertised. Good Luck.

YZ450 fork seal instructions

Ok. There has been a number of post before that have been very helpful to me, but there have been a few key points that have been over looked. I dont know if these were because they were working on the old 426 and not the 450. But here we go.

Step by Step:

- Loosen fork caps before removal, 19mm

- Remove tire and axle

- Remove forks from triple clamps

- Unscrew caps from outer tube

- Drain out the fork oil, guys please dispose of correctly

- Slide outer tube down far enough to get "special" thin wrench between spring and cap (17mm)

- This does not need to be a "special" thin wrench, just push the spring down with one hand and slide a standard 17mm on.

- Once taken off remvoe the spring.

- Remove dust scraper from bottom of outer tube (small screwdriver to carefully pry off)

- Remove wire ring clip from outer fork tube (I use small flathead screw driver or small needle nose)

- Then, here comes the "scary" part, the manual says to yank on the outer tube until the outer and inner tubes come apart. Yikes. It's freaky the first time but as long as you've removed the spring clip they comes apart. If your not very cordinated you may want a 2nd set of hands.

- Take off the slide metal and piston metal, inspect them and if they look ok, re-use them. Otherwise replace.

- Then the seal and dust scraper just slides off the top of the inner tube.

- The manual has a good suggestion about placing a bag over the inner tube before you put the new seal on, this protects it from getting scraped by the sharp tube edge (I used the bag the seal came in coated with some fork oil).

- Put the new dust seal, then fork seal, washer, slide metal then piston ring (the piston ring clips on at the top and should not move)

- Now this gets tricky a bit. You need a fork seal drive or a home made one. Use a 2" piece of PVC about 4-6" long. Cut about a 1/4" wide piece out of one side all the way down. And the other side cut down till about 1/2" from being cut in half. This will allow a tight fit over the inner tube and will let you get inside of the outer fork. I tapered the inside of mine and use a metal clamp as opposed to a zip strip (I WILL POST A PICTURE OF MINE TONIGHT).

- Slide the inner into the outer tube with the dust+fork seal at the bottom of the fork (by the axle side).

- Put your "PVC seal driver" on between your washer and fork seal. You have to drive the slide metal into the outer tube.

- Then remove driver and place between fork deal and dust seal.

- Drive seal into outer tube.

- Re-install the fork clip. It should go in real easy into the grove. You may need to press the ends down with a flat head to pop it in. NO FORCE NEEDED.

- Slide dust seal on. And check for smooth movement.

YOUR ALMOST DONE. Now comes filling the fork oil

- With the forks compressed and SPRINGS OUT fill the forks with fork oil TO THE TOP. I used Bel-Ray 7w.

- Do like the manual says. Move the piston slowly up and down about 10-20 times. Let set for 15-30 minutes to let air bubbles out.

- Re-fill to the top of the forks again and pump the forks slowly no more than 7.9". Pump them about 10-20 times. You may need to do this a few times. Let the forks sit for about 30 minutes each time you have to add more oil.

- Then use a fork oil leveling tool. I use a top of and old widex bottle and cut the tube to my desired length. (I'LL POST THIS ALSO).

- Once you have your oil at the desired height put your springs in and put the cap and stuff on like you took it off.

- One good trick and a good idea by one guy is after you have them all assembled to loosen your pressure relief valve and compress the forks as far as you can then hold them there and close the valve. This creates a vacume and will collapse the remainder of the air bubbles.

This is how I did mine. Now that I have done it I would never pay for someone else to do it. I could easily change my seal in under and hour now.

Also replace your Yamaha fork seals and dust caps with Honda CR 125 parts. They fit better and do not break as much......

hey twnstngrip, that's a good idea about using the windex bottle. Or you can use one of those round connectors with a thumb screw and use that. Then you can change you're oil hieght as desired. Owell, your way is aweome too, I'll use that next time. :thumbsup:

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now