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Fork Seals

Before you replace your seals, try this from Dale Horstman - COG digest 2315

Stephen McGloughlin wrote:
My new (to me) '92 Concours, 21K miles, has just started to leak fork fluid. Dealer has quoted $80 for parts, and $200 (incl. parts) to do the job. Anyone have advice on this?

Dale replied
What kind of shape are your fork tubes in?  If they are still smooth, no pits or rusty spots, no sharp edges to tear up a seal, then you might not have to replace the seals.  They might just be dirty. Take a wide roll of masking tape (wider is better, 3"+) and stick a layer of masking tape around the fork tubes, just above the seal.  Hop on the bike, grab the front brake, and gently bounce the front end up and down a couple of times, forcing the tape down into the seal.  Notice the nice black ring of dirt the masking tape pics up?  That might be the reason the fork is leaking a bit.

Clean everything up, and go ride for a couple of days.  If the seals stop leaking, you are in good shape.  If not, then you'll have to replace the seals.

Good luck!  Thanks to Don Damron for clue-ing me in to this trick.

And if you must do the deed:

COG Digest 1963 Date: Sat, 5 Aug 2000
From: "Roman, David E (Dave)"

1.  Should I attempt this repair or not?
Yes!!! it's easy did it myself for the first time a few weeks ago.  I have an 86 but I suspect the forks are quite similar except for the lack of drain holes in yours.

2.  How do I remove the current fork oil seals?
Take the front wheel, fender and brake calipers etc. off. Find the allen bolt that goes up into the bottom of each fork leg and loosen it. This is easier with the spring still in the fork. Once it's loose, you should remove all the spring preload to prevent the fork leg from slamming down hard when the bolt is removed (I think, either way it won't hurt). If the bolt turns but does not come out or loosen, you'll need to use the broom stick method or make a tool to hold the part ("thingy" from now on) that the bolts threads into and keep it from turning. I made a tool out of  three feet of 5/8" threaded rod with a nut threaded on to end about 6 inches from the end. I drilled through the nut and rod and pinned it in place with a nail. You could just use two nuts and jam them together instead of pinning the one nut.

To use the tool/broom stick, take off the fork cap and remove the spring and spacer if it's got one. Carefully slide the tool/broom stick into the fork until it makes positive contact with the "thingy" at the bottom of the fork. The nut on the tool should fit inside the "thingy" as though the "thingy" were a 12 point socket. The broom stick will need to be jammed in. Making a taper on the end would help with this endeavor.  Get a helper to hold the tool/broom stick from turning and finish removing the allen bolt.

Carefully pry up the dust seals on the fork legs and slide them up out of the way. The spring clip should now be visible. It's probably rusty and covered with crud. Remove it and then use the fork leg as a slide hammer to pop the oil seal out. Once it's out you can remove it from the fork tube by removing the bushing and some other minor part(s) I cannot seem to recall.

3.  Is there a special tool required to set the new seals?
PVC pipe is perfect for this and making potato cannons. I think 2" is the correct size but it could be 1 1/2".  Anyway, cut off a 2" long section of PVC pipe at exactly 90 degrees and remove about 1/3 of the pipe so that from the end it looks like the letter C. Put the dust seal back on the fork tube if you ever removed it. Put the new oil seal on the fork tube and re-install the bushing and part(s) from step 1. Snap the C shaped PVC pipe with the 90 degree cut facing down, over the fork tube and below the dust seal. Put the 1/3 that you removed back in it's place and clamp the whole thing in place with two hose clamps.  Clean out and lubricate the top of the fork leg so that the new seal will slide into place easily. I used some 400 grit sand paper to remove the corrosion. Use the fork leg as a slide hammer and the PVC as an anvil and the seal should go right in.

4.  Since I will have the entire front suspension apart,  what else should I  do preventative maintenance on?
Shim the bushings if needed. Don't know how. Put in Race Tech cartridge emulators and springs. Polish the fork tubes. Remove any nicks in the fork tubes. Use Bel-Ray fork oil as this supposedly has some chemical in it that swells the fork seals and keeps them from leaking.

5.  What setting should I dial the adjusting screws atop the fork tubes once everything is back together and lubed up?
Same as before you started unless you changed the springs. If you changed the springs follow their manufacturers advice

I may have forgotten some crucial bits so refer to your shop manual and get advice from someone smarter and less forgetful than me before attempting this job.


Article By: David J. Morrow

Original August 2001 

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