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Old 12-02-2012, 05:46 PM   #1
RaystheBMW OP
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Fork seals - What's causing this?

I installed new seals for the first time a few months ago, and the fork keeps seeping oil on both sides. Stanchions are smooth as a baby's behind, and using 300cc Motul 10W. Why is it making this mess?

Are the seals installed upside down?

RaystheBMW screwed with this post 12-02-2012 at 05:53 PM
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Old 12-03-2012, 03:39 AM   #2
rambozo
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Kinda hard to see on my iPod but they look
upside down to me

The flat side should face up
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Old 12-03-2012, 05:05 AM   #3
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I'm thinking that too, because the visible edge looks more like a wiper. But if I turn it over, that would put the sphincter spring facing outward, which goes against everything I know so far about seals.
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Old 12-03-2012, 07:10 AM   #4
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Maybe im not seeing the photo clearly enough and you have
them in the right way

On my /7 seals the spring was on the inside, although on
my bandit they're on the outside
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Old 12-03-2012, 07:20 AM   #5
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Is the fork oil getting past the seal at the tube or at the slider?

Seals are in straight, with no nicks or cuts? Meaning, they went in w/out trouble?

Part # checks out?

Fill cap & top nut is tightened?
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Old 12-03-2012, 09:54 AM   #6
georgesgiralt
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Are you sure 300 cc is the exact amount of oil ? If too much oil is put into the fork, the gasket can't cope with the excessive pressure this will cause....
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Old 12-03-2012, 12:57 PM   #7
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The 300cc oil quantity was confirmed in 2 places, in a manual and online. The seals are an updated version that require a shim sitting on top to keep the dust cap from interfering with the thicker seal. The top fill screw and nut are tight. I didn't consider the possibility of oil running down from somewhere above, or from around the outer perimeter of the seal. I'll take a closer look later. I have a tough time wrapping my brain around the inner functioning of the tubes and sliders, and where the oil circulates to.... I'm sure I'm over-thinking it. So far the only symptoms are a dirty oil line on the tubes at the top of the slider travel, and eventually after a couple rides, the dribble seen in the top photo.
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Old 12-03-2012, 01:13 PM   #8
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Sometimes the fork braces require adjustment to allow proper leg allignment. If the brace isn't correct and is causing misallignment that may contribute to a leak

The easy test is that with the wheel off, the axle should slide fully home with light finger pressure. If you have to push hard, something is amiss
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your bike is suitably dirty. Well done.
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Old 12-03-2012, 02:30 PM   #9
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You might also consider a lighter oil. Those bikes originally came with 5 weight. A lot of people have gone to 7.5 for road use. Some have gone heavier for racing. I tried the Motul 10W in my 82 R100 and did not like the feel of it. Went to 7.5 and it is much smoother. At least to me.

Heavier oil can cause seals to weep or leak if ridden aggressively.

I would also recheck the installation of those seals.
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Old 12-03-2012, 02:41 PM   #10
Big Bamboo
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Another thought, "smooth stanchions" could still be worn out of spec.
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Old 12-03-2012, 09:23 PM   #11
RaystheBMW OP
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Quote:
Originally Posted by SOLO LOBO View Post
Sometimes the fork braces require adjustment to allow proper leg allignment. If the brace isn't correct and is causing misallignment that may contribute to a leak

The easy test is that with the wheel off, the axle should slide fully home with light finger pressure. If you have to push hard, something is amiss
The axle slides in and out easily.

Tonight I checked and there is no oil leaking from the top, so definitely from the seal area. I ran a thin feeler gauge around the seal to maybe dislodge any crud that gathered in there.
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Old 12-04-2012, 06:09 AM   #12
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This may not matter but, when you initially installed the sliders w/ new seals did you have a thin film of fork oil on the tubes?

BTW, this is a K bike type front end?

You replaced the seals because they were also leaking, I presume & not as a preventative measure?

I recall my K75 seemed to eat fork seals. Are you certain your forks are straight?
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Old 12-04-2012, 07:23 AM   #13
RaystheBMW OP
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The tubes were oiled and I put a light coating of grease on the seals. Yes the later R65 came with a early version of the K bike fork. I'm starting to think my dad had a devil of a time with the oil leaking. He, or somebody, tightened the bejezus out of the top fill screws. And the greasy gunk all over everything when I got the bike was probably fork oil that kept getting replaced. It has only 22K miles, so I'm thinking wear on the metal parts is not a big issue.
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Old 12-04-2012, 02:00 PM   #14
tofgasp
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Your seals are not upside down. As stated above, you might have an alignement problem of your stanchions wich is quite common on these forks.
The sliders are not guided as well as in the early models, but just by one teflon ring and 2 small o-ring. You must absolutely reassemble the fork in a specific order otherwise the fork brace twist the tubes, same as the wheel axle, if you tighten the lage bolt before the ones on the sliders, they lightly bend.
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Old 12-14-2012, 04:55 AM   #15
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Quote:
Originally Posted by tofgasp View Post
Your seals are not upside down. As stated above, you might have an alignement problem of your stanchions wich is quite common on these forks.
The sliders are not guided as well as in the early models, but just by one teflon ring and 2 small o-ring. You must absolutely reassemble the fork in a specific order otherwise the fork brace twist the tubes, same as the wheel axle, if you tighten the lage bolt before the ones on the sliders, they lightly bend.
I'm having the same problem on my R100RT with Type V forks. I pulled off the gators and they were pretty much filed with fork oil. I just bought seals (bike is new to me I don't know if they've ever been replaced), but I don't know the assembly/alignment proceedure . Know of a good guide?
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