Fork seal replacement. With photos.

[marc]

Step 1: Place your bike on jacks, remove wheel, caliper, fender, and Odometer counter cable.



Step 2: Mark the tube. This is specially interesting if the bike is quite old and the tubes may have a slight bending.
While the fork still in the bike, loosen the fork top cap.



Step 3: With the fork removed, unscrew the top cap with a 1/2 wrench. Since there is some spring pressure tht may damage the cap threads (aluminium), apply press to the fork while turning the cap.



Step 4: With a screwdriver remove the fork dust seal and the circlip. Apply WD40, it will ease the oil seal too.



Step 5: Unbolt the fork bottom. It is not as easy. You need to lock the inner threaded part that the bolt is inserted.
You'll need to build yourself a locker tool as follows:
- Bottom fork locker: cut a 52mm (or longer) piece of threaded M16 threaded rod. Place 2 nuts in each end and tighten them to lock themselves to the rod.
- Use: Insert one end of the "tool" inside the fork. You will feel that it engages the M24 shaped part at the bottom. Plug the other end to a M24 socket attached to a T wrench. The 52mm allow to reach out of the fork.



Step 6: After removing the bottom bolt, pull the fork tube several times, hitting the seal out.
Once removed inspect bushing. Reassemble in the same order.
Replace the oil seal. Part number: Ariete 027.
Take care if your top fork is dented, it may damage your new oil seal.



Step 7: To press the oil seal to the place you'll need to press it. Use some cheap 30cent PVC tubing accessories. I managed to find some pieces of 40mm to 40mm PVC pipe coupler to fit perfectly. They are 40mm inner diameter, 46 outer diameter. Bought several as seen in the image.
Place the fork cap: you don't want any debris to fill inside during the hammering.
Use a piece of wood and a plastic hammer. Hit hard.



Step 8:Drop oil inside the fork. I used SAE15.
For original springs, drop 389ml. For Progressive springs, I dropped 350ml.
I used a cheap baby feeding bottle as a "precision" measure bottle. Works perfect and cheap.



Step 9: Fine adjusting the oil height.
With the fork fully bottomed, without the spring, drop oil until there are 99mm from the oil to the top of the fork.
Since I am using Progressive Springs springs and they displace more oil, I need to drop oil until the oil height is 140mm below the top of the fork.
I used a plastic tie strap with a mark at 140mm, as a dipstick, as somebody else reccomended here



Step 10: Install the spring and the spacers. If the spring is  progressive, install the thick threaded part of the spring upwards to prevent displacing lots of oil.
Close the cap: apply pressure while turning the cap: it is aluminium and it is easy to damage the thread.

[herennow]

Thanks for taking the time to write this up.

The only thing that I would add is that when replacing the oil seals one should seriously consider replacing the fork bushes at the same time. They are a wearing item and on older bikes where fork oil was not changed, the Teflon is probably shot which leads to aluminium wear particles in the oil. These oxidise and Aluminum oxide =sandpaper grit.  For 50 bucks you can renew everything and forget about it for another 15 years.

*edit* looking at the photo of your bushes on my PC (saw on phone before) - the bottom one is very worn, the coating is almost all gone. The top bush looks worn but that is the rear side (non sliding) but I'd guess that the other side, the sliding surface, is as worn as the lower. I'm sure you did replace them after inspection - this will eliminate stiction and rapid wear.
Cheers

[sledge]

You should also replace the copper sealing washer on the bolt at the bottom 

[Arpee]

Thank-you for posting this!  Love the make-shift seal driver--very clever!

[J_Walker]

ill do fork seals all day long. both regular and Spanish forks. now that I have my "tool"

[Codoloco]

This should be in the wiki

[Carltheproducer]

Please read my thread to see the quickest way to break the damper rod bolt from nut inside forks. http://gstwins.com/gsboard/index.php?topic=72508.0