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CBR900RR, SC28, front shock seal problem

2K views 15 replies 5 participants last post by  superhessu 
#1 ·
first message to this forum, but anyways... Hi!

I ran into some trouble replacing oil seals on my '92 CBR900RR front shocks. One of them was leaking oil from between the dust seal and the shocks, and now that I disassembled it I think I know why: by the looks of it, the previous owner(s) seems to have tried to pry the seal out by hammering a flat head screw driver in between the seal and the fork tube, or something similar... I replaced the seal anyway in hopes that it would solve the problem, which it didn't.
In my haste I forgot to take a picture of the situation, but imagine aluminum hammered with something sharp and you'll get the point.

So now I'm looking at buying new forks, or repairing the old ones. This brings me to my question: have any one of you guys tried to fill in the scratches on the sealing surfaces with some kind of substance, say, bondo or something? Or am I better off just buying "new" used shocks from ebay?
 
#4 ·
I have something called stud and bearing fit which is a kind of thread lock glue that takes up a *small* amount of extra space in lightly worn bearing housings. Might be worth a go?
 
#5 ·
Thanks for the suggestion, didn't realize there's this kind of a product going around too!

However, I doubt that it'll solve the issue since the pits I have are like 1½ mm deep in some points, with a width of 2 mm and the length is all the way along the sealing surface (about 10 mm or so?). Problem is that if I wanted to try that glue now, I'd have to go for a new pair of seals and oil again, so I'd need a little more confidence towards the glue actually working in my case... just wouldn't want to spend any more money to a fix that might have around, say, 50% success rate maybe?
 
#6 ·
Yikes that's a proper gash. Probs weld and lathe the only good solution and if you go that route might as well get a pair of used pumps.

Nice nick btw, Finn I presume? Where from?
 
#8 ·
The gouges are in the aluminum. So the chrome stanchions are ok, just the fork outer body that holds the seal is damaged? Is this correct?

If that is the case then you can fix that with good quality epoxy and some careful filing or sanding.

If the gouges are in the stanchions there are fixes for that, too, but it sounds like your trouble is with the area the seal sits in vs the area the seal rides against.
 
#10 ·
Both of the chrome slider tubes are actually in surprisingly good condition, there's no issue with them. The problem is, like you said, with the area in which the seal sits in.

Based on this answer, I think I'm going to give it a go one more time and try an epoxy fill. And I'll try and remember to take photos this time around :) I'm thinking maybe putting in the old seals to act as some kind of a mold for the epoxy to sit against, just need to figure out some release agent so that I don't accidentally glue them in there. Or remove them before the epoxy sets completely.
 
#11 ·
#13 ·
Ach soo... I thought the gash was in the SLIDER and wondered what sort of caveman og has swapped the seals the last time...

https://www.biltema.fi/autonhoito/autonhuolto/autokitit/kemiallinen-metalli-2000019604

I'd thoroughly rinse the area with some high vapor solvent, let it air out then give that stuff a toss, fairly thick mix, some sort of a molf is probly a good idea.
That's a good suggestion, I might try that instead of epoxy. Got all sorts of thinner and acetone cans laying around so cleaning's not a problem.

Trying to use the seals as molds is asking for complications IMO. Just dab some epoxy where needed and dress it back down. Simple is good!
That might be, but the area of damage is quite large. I guess it depends about how easy it is to make a mold of some sort there.

I took apart the shocks today, but hadn't time to actually do anything to them yet. But now I got a picture:


This is what I'm up against here. Hopefully I'll be able to try the fix at weekend.
 
#14 ·
Personally, I would file down any high spots and fill it with epoxy. You could also just install the seal with some Threebond or something, but that's just gonna glue them in and make it even harder to disassemble in the future. A less adhesive sealant like silicone would come apart easier, but I'm not sure it'd trust it.

The repair doesn't have to be machine shop smooth. The seals can accommodate a fair amount. If it were mine, I would use the original formula JB Weld to fix that.
 
#15 ·
So, a small update to the situation.


I used Loctite's 5min epoxy, since I had it around. Working time was plenty enough for such a small area.



This is how things look like after one day of glue hardening, and after some sanding with #120. I used a small needle file to level out the surfaces, cleaned with acetone, and then applied the glue with a small wooden stick and good'ol fingers. Turned out making a mold would've made things too complicated / time-consuming / messy.

After 1 day of hardening the glue still had enough tackiness to constantly clog the sand paper I used, so I decided to give it a one more day until I ram the seals in, and because it was getting late. I'm a bit worried that the glue isn't going to fully harden in a while still, and it might shrink a little while doing that, but I'm going to put the seals in regardless. Probably going to use some additional sealant adhesive too for extra insurance, gotta see what the hardware stores around here have.
 
#16 ·
All's done now:


I pumped the front end for a good amount of time and there's no leaks. I used Loctite's silicone adhesive to secure the seals in their place - don't remember the exact product, but I think anything similar would've worked as well.


Here's the patient. Still alot of stuff to do, but I'm hoping to get it up and running so that I can get atleast a few kilometers of driving for this season. No plans for any serious modifications, I'm thinking of keeping it as much original as possible.

Thanks to all of you for the suggestions you gave in this topic! As an afterthought I feel stupid even thinking that this kind of an issue could not be solved without buying new shocks.
 
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