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Front Fork Oil Seal Replacement - One Tip

18K views 24 replies 15 participants last post by  Solo  
#1 ·
Scenario: 2008 Wee, aka “Toothless”; 31K on the odometer; right front oil seal leak

Tip: During reassembly, use the oil seal spacer to press fit the guide metal bushing into the fork cylinder, after inserting the fork tube and slide metal bushing into the fork cylinder.

Long Version: I've had "Toothless" since Sep 2012 and I noticed a leak in the right front seal about 3 months ago. I performed the 35mm clean-out trick which bought me a couple of extra months. Last week, when the seal started leaking again, I tried the film again, to no avail.

I knew I needed to replace the front seals and planned on following Black Lab’s excellent tutorial, Replacing Front Fork Oil Seals << Black Lab Adventures.

The disassembly of the fork went as expected. The reassembly is where it got tricky, specifically with the guide metal bushing and slide metal bushing interplay. I inserted the guide bushing as directed, then tried for the next two hours to get the slide bushing to fit through the guide bushing as indicated in this section excerpted from the tutorial:

Using a finger, I coated both the “guide metal” and the “slide metal” with a film of fork oil. I then carefully slid the fork tube back into the cylinder. I found that I had to use some pressure, and a “twisting motion” to have the “slide metal” work its way through, and by the “guide metal”. This is a snug fit!”

With no way simple way to get the guide metal bushing out and the slide metal bushing deforming, due to multiple attempts to force the slide metal past the guide metal, I realized I had a problem.

First, I focused on removing the press-fit guide metal bushing. I was able to wedge a thin flat blade between the guide metal and the wall of the fork cylinder. Using a twisting motion, I pried the lip of the guide metal away from the cylinder wall and removed the bushing. Having no replacement guide metal/slide metal bushings, I set the fork assembly aside and focused on the other fork.

Disassembly of the second fork followed the guide exactly. After cleaning all the parts, I worked through the reassembly in my mind. I realized that if I inserted the fork tube, with its slide bushing into the fork cylinder, prior to pressing in the guide bushing, I could use the oil seal spacer to press in the guide bushing. Two minutes, and a couple of hammer taps later, I had the guide bushing correctly seated in the cylinder and completed the fork reassembly.

Moral of the story: Every tutorial is a labor of love, but only represents that individual’s experiences. As is said all over the forum, YMMV. I would never have attempted the seal replacement without Black Lab’s tutorial and as a bonus, learned a valuable lesson in the process.
 
#2 · (Edited)
I realized that if I inserted the fork tube, with its slide bushing into the fork cylinder, prior to pressing in the guide bushing, I could use the oil seal spacer to press in the guide bushing. Two minutes, and a couple of hammer taps later, I had the guide bushing correctly seated in the cylinder and completed the fork reassembly.
What you have written is the correct way to do it. And, that is the way I have done it too! I will change that step in the tutorial.

I appreciate you catching this!

Sincerely,

Barry B.
 
#4 ·
Thank you Black Lab for putting this tutorial online. Between this and the service manual I managed to replace both seals. For somebody with three left hands that was a good result. Two things that might help other people. I had to wait a week to get my oil seals. While I had the mudgard, fender, off I cleaned up where the fender bolts are then I used contact glue to glue the fender bolts in place so when I went to reattach the fender it was really easy to do. When I put the new oil seal in I had cut about a half inch,1.25cm, out of the old seal and used that to put the new seal into its seat. I pushed it down on the new seal as far it would go. Then used a screwdriver on the old seal to push the new one into its seat. Then hooked the old seal out with the screwdriver. It worked perfectly and at no risk of damaging the new seal. :thumbup:
 
#5 ·
years later

I have to add my thanks for the help. I used the old seal along with a piece of 1 3/4"pvc, split down the middle, a little over a foot long and pounded on the old seal, and the old seal came up with the tube, put the snap ring in place.
Done, 2009 650
Thanks again
 
#8 ·
I was following the Black Lab tutorial but brain farted putting in a part out of sequence. I heated up the fork lower with the propane torch until the part fell out when tapping it on the vice.
It helps to read it several times and get all the parts in the proper sequence to avoid the brain farts.
Other than that it's a fairly simple procedure.
 
#9 ·
I'm about to do this procedure for the first time. I often see references to the "slide and guide" bushings being replaced during this procedure. What are the wear indicators I should be looking for to know if this is needed or not? Some folks talk about it like it's required every time, while others liken those pieces to something like the washer on your car's oil drain plug....A.K.A., only replace when needed, not every time.
 
#12 ·
Using a ratchet strap to load up the springs will often get rid of the need for an impact wrench.
 
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#13 ·
If I am not going to change out any parts other than the oil seal and dust sheild why do I have to open the fork spring bolt. I mean I could just use a dental pick and gently manouver the oil seal out on either side. Then change the oil and never have to touch that torqued fork bolt ?

I have heard that some dirt guys just put a screw into the seal and pull itout that way. To put the seal back in you put some plastic tape 2mm tall round the fork leg and pop the seal in, then add your fvourite oil and bobs your fork?
 
#14 ·
While the method you describe sounds like it could save time, I found that short cuts are not always the best or safest solution.
How do you know how much oil has been lost due to the leaking fork seals?
Since the forks have to be removed from the triple tree / yokes to replace the fork seals, a complete fork service is recommended.
 
#15 ·
Interesting point, I have purchased the impact gun anyway. I was going to change the fork oil also as I want the same oil in both forks once done. Thats not difficult but that fork bolt is.

I also read that the application of marine grease to the inner oil seal will help prevent entry of water (marine grease does not washout due to water) as an added precaution.

It seems that the left front oil seal blows out sooner than the right from reading various posts is this..... an assemble line issue? :unsure:
 
#16 ·
Don't use grease.

Grease moves too slow and can try to turn the seal inside out.

I put a strip of green kitchen scourer between the dust seal and the oil seal, it will help collect any crud that gets past the dust seal.

I change it after a muddy ride or a few times a year.

While you have the forks off fit fork gaiters, I like the neoprene ones. (this is harder to do if you have a fork brace)
 
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#18 ·
Grease on a spinning seal is the right thing to do but not on a quick moving sliding seal, they are built to hold back oil only and a given grade of oil depending on the application.

What has saved your seal is after a few strokes the fork oil will have mixed with the grease and started thin it out

Grease will do nothing but collect crud then turning into grinding paste.

Have a look in your repair manual they don't ask for grease.
 
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#19 ·
I'd never put grease in fork seals, or any seal that isn't intended to hold back grease. If you wanted to proactively lube the lip for assembly, it's probably safe to use fork oil itself.

Making fork seals last is as simple as wiping off any stuck-on bugs or crud before every ride using a wet cloth. Mine have 90k miles under them.
 
#20 · (Edited)
Bike on a lift, if the fork caps are removed, how hard is it to get them back on?

Edit
Now I realize this is a dumb question. If I screw the preload adjusters all the way out, it should be easy.
 
#24 ·
Automotive rear axle bearings are lubed by the gear oil from the diff. They go in dry. If you pack the roller bearings with axle grease, which seems like a smart thing to do, they fail prematurely. Maybe a bad example, but think about using grease when it isn't called for.