Author Topic: Fork leak when bike is sitting  (Read 818 times)

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Offline DC Concours

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Fork leak when bike is sitting
« on: July 22, 2017, 03:38:34 am »
My left fork has had a little "high water mark" kindda leak for a year. Anyone know why a fork would leak few drops sitting under a tarp for 2 weeks? Does that mean that there is too much oil to begin with? Or did the 100 deg temps have anything to do with it.


I found a couple of drops on the ground under the left fork. Is is possible to get oil on the pads if oil flows down like that. I didn't see any but to ruin a pad only a little bit of oil is needed.

Offline Jerry_Layman_NE

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Re: Fork leak when bike is sitting
« Reply #1 on: July 22, 2017, 09:12:59 am »
Yeah, it's time for a fork seal job.

It's (apparently) not too hard of a job to do yourself, but I've always just removed the forks and brought them in to the bike shop to have the seals done. Lots less expensive this way as compared to just bringing your bike in and say, "Fix that sucker!"

Good luck!
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Offline ErikB_76

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Re: Fork leak when bike is sitting
« Reply #2 on: July 22, 2017, 11:02:35 am »
Sometimes some dirt can get on the seal face and cause a small leak.

I think its worth trying a sealmate to remove any dirt.
Clearly someone could make such a device or cyclegear has them for a few bucks.

http://sealmate.net/

If it still leaks, replace the seals.
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Offline RWulf

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Re: Fork leak when bike is sitting
« Reply #3 on: July 22, 2017, 01:36:30 pm »
In times passed we would take a peace of 35mm film slide it
down the fork tube into the seal and with a rotating upward
movement try to remove any dirt. If you try this and it still
weeps it's time for new seals.

Offline alan

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Re: Fork leak when bike is sitting
« Reply #4 on: July 22, 2017, 03:54:15 pm »
I just used the 35 mm film trick on the right fork of my '11 Versys 650. Got the edge of the film up under the dust cover and seal, and while rotating it around the fork tube I got quite a bit of gooey sandy grit on the film. The next ride pushed the excess oil out from under the dust seal and now it's not leaking. I've used this trick a number of times over the years, mostly on off-road bikes. I'm sure there is a youtube vid on this somewhere....  Happy Motoring.      :great: 
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Offline DC Concours

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Re: Fork leak when bike is sitting
« Reply #5 on: July 22, 2017, 03:59:21 pm »
Thanks. I will do that.

But how high is the oil in these forks? It is filled up to the brim? Should the forks leak if the bike is left parked for a few weeks. I know when I parked it on the side stand it was not leaking. Now after a couple of weeks there are a few drops. How does it leak from the top against gravity if it is not over filed. Am I wrong?

Offline SalNap

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Re: Fork leak when bike is sitting
« Reply #6 on: July 22, 2017, 06:09:59 pm »
They could have been over filled on the last service. The pressure from being on the stand might have been just  enough to  push the oil to the seal, which could have a tiny bit of grit / sand allowing it past ....
Try the film if you can. Not much of that around since digital cams...
I read where a guy cut the shape of the  "seal saver" out of a laundry detergent bottle.

I've used the 35mm film with success

If the fork oil hasn't been changed yet, its probably over due. Its not that hard of a job if you have a repair manual

Offline Steve in Sunny Fla

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Re: Fork leak when bike is sitting
« Reply #7 on: July 22, 2017, 07:14:30 pm »
When the forks are fully extended, there is appx 11" air gap down from the top. Compressed, it's about 6" . So yeah, the oil is higher than the seal. steve
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Offline DC Concours

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Re: Fork leak when bike is sitting
« Reply #8 on: July 23, 2017, 12:17:50 am »
ok didn't know the seal was bathed in oil all the time. This makes sense then. If there was a drain plug I would drain some oil out. The oil shocks suck to begin with and I don't need it.

Offline Kelly E

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Re: Fork leak when bike is sitting
« Reply #9 on: July 23, 2017, 04:28:34 am »
The clear plastic that they use on the secure packaging works real good for cutting seal savers out of.
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Offline alan

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Re: Fork leak when bike is sitting
« Reply #10 on: July 23, 2017, 06:21:56 am »
Well DC, I guess you could go with a springer front end and do away with all that messy useless oil stuff. Maybe just drill a hole hear the bottom of the fork and let the oil out.... call it "atmospheric cushioning".   :rotflmao: 
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Offline SalNap

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Re: Fork leak when bike is sitting
« Reply #11 on: July 23, 2017, 10:51:51 am »
That would make for a pretty harsh ride.

Hope for the best, plan for the worst.
Try the film or seal saver method. Could just be one speck of dirt stuck there...
Just like float needles.... one speck is all you need....

Worst case is replace seals, fresh oil.
I'd do bushings while I was in there. Cheap parts, last time I did forks I believe seals/dust caps/ bushings / oil was probably a $50 job , couple hours of my time

« Last Edit: July 23, 2017, 10:58:56 am by SalNap »

Offline WillyP

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Re: Fork leak when bike is sitting
« Reply #12 on: July 23, 2017, 01:45:41 pm »
The oil shocks suck to begin with and I don't need it.

 :-\

The oil and mechanical spring work together to supprt the bike, as well as provide dampening. Without the oil, there would be a much larger volume of air in the fork, which would allow the bike to bottom out more frequently. The spring by itself is not strong enough, it relies on the compression of the air in the fork to prevent bottoming.
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Online MAN OF BLUES

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Re: Fork leak when bike is sitting
« Reply #13 on: July 23, 2017, 06:15:12 pm »
ok didn't know the seal was bathed in oil all the time. This makes sense then. If there was a drain plug I would drain some oil out. The oil shocks suck to begin with and I don't need it.

Why would you "drain some oil out" unless you actually knew how much oil was in them to start with???
This sounds very silly.
Ther are set procedures for measuring that level in the FSM
With forks extended on pre 94 "air assist" forks,, or '94 and up non air assist with foks compressed... with springs removed from both versions...

As for the "air" in the forks playing an active role in the function, and smoothness, of post '93 forks... it has no function, or bearing on their operation whatsoever.
The seals on the top cap are only there to prevent contamination of the oil in tghe tubes, not to provide any other operational benefit

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Offline DC Concours

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Re: Fork leak when bike is sitting
« Reply #14 on: July 23, 2017, 07:28:19 pm »
hahaha. I was going to drain some of it out so that it won't leak-- steve said that the oil seal in bathed in oil.

And I don't think the oil does anything for me. The forks dive anyway. They suck.

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Re: Fork leak when bike is sitting
« Reply #15 on: July 23, 2017, 09:56:35 pm »
hahaha. I was going to drain some of it out so that it won't leak-- steve said that the oil seal in bathed in oil.

And I don't think the oil does anything for me. The forks dive anyway. They suck.

The oil controls rebound damp speed.
Springs contol the "dive" depth and rate.

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Offline DC Concours

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Re: Fork leak when bike is sitting
« Reply #16 on: July 23, 2017, 10:32:28 pm »
I think it is time to take my bike to Matt and have him do the spring cutting/adding thing I have heard before.

Offline connie_rider

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Re: Fork leak when bike is sitting
« Reply #17 on: July 23, 2017, 11:57:10 pm »
As for the "air" in the forks playing an active role in the function, and smoothness, of post '93 forks... it has no function, or bearing on their operation whatsoever.
The seals on the top cap are only there to prevent contamination of the oil in the tubes, not to provide any other operational benefit.

The oil controls rebound damp speed.
Springs control the "dive" depth and rate.


Whoa,,, MOB, I'm not a suspension expert. Far from it..
             Most of the time, I take my hat off to you on mechanics,
               But, I don't agree with your statements about the air in the fork tubes.
               I think the oil level and size of the air pocket above the oil is pretty important.
                {Fork compression builds pressure in the fork tube}
               
WillyP' s statement is closer to what I think...
But I'll add, the pressure of the air in the forks {indirectly} contribute to damping.
   ie; A contributing factor to how quickly fluid moves thru an orfice, is the pressure on that fluid.

WillyP sed; The oil and mechanical spring work together to support the bike, as well as provide dampening. Without the oil, there would be a much larger volume of air in the fork, which would allow the bike to bottom out more frequently. The spring by itself is not strong enough, it relies on the compression of the air in the fork to prevent bottoming.

NOTE: We're not arguing here,,, we're "discussing" how air effects the front suspension.

Ride safe, Ted
« Last Edit: July 24, 2017, 12:35:52 am by connie_rider »
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Offline Steve in Sunny Fla

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Re: Fork leak when bike is sitting
« Reply #18 on: July 24, 2017, 12:05:53 am »
DC, your stretch pants must have gotten to tight and it's cutting off the blood to your head  ;) If you don't like the damping (who would)_ you can change the viscosity at the same time you do the springs. Matt can get you hooked up. Steve
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Re: Fork leak when bike is sitting
« Reply #19 on: July 24, 2017, 12:25:47 am »
Ted, I'm no eggspurt either, but I have done some tests, and also was an engineer in my pre retired life... with some hydraulic experience tossed in thruout,

Well, we can agree to disagree, and that is fine.
Until you have "tested" your theory, by viable means, I will still disagree..

I say this based on the fact that the 2 C10's I owned, one still in my garage, and both were pre 94 versions with air assist and crossover tubes intact, that I installed Progressive springs in... and ran them, both without the valves in the schrader fitting... showed absolutely NO difference whatsoever in the function, damping, or handling charecteristics of either bike.
I'm saying that I ran BOTH with an open to atmosphere fork to test, and then after that installed a simply plastic valve stem cap, with an .030" hole drilled in it, afterwards, I also tested with a stem cap undrilled prior, and only threaded it on 1-1/2 turns... it never blew off under extreme conditions.. forks never bottomed before, or after either test. I took it much further tho, because that's just the way I am...
I attached a low pressure dial air gauge to the scrader fitting, and ran the bike slamming the forks to the max, and never saw a 2 psi hit on that gauge, and I think it was more of the gauge needle bouncing, than the actual pressure surge.
Sorry, but I'm not gonna say it makes any discernable difference... take the bike up tom of Mt Washington, or Pikes peak, remove the caps, re.install them,.and ride back down an along the coastline of the ocean... will that make a difference?
Hypthetical question. :beerchug: :beerchug:
« Last Edit: July 24, 2017, 12:28:56 am by MAN OF BLUES »

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Offline connie_rider

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Re: Fork leak when bike is sitting
« Reply #20 on: July 24, 2017, 01:14:55 am »
Thanks MOB. Yea, lets agree that we disagree...

On the C-10 I'll agree, changing the oil level by 1/2" or so doesn't make a lot of difference.
I was disagreeing with;  your statement air has no function, or bearing on their operation whatsoever.

NOTE: Someone could calculate the pressure increase by figuring the pocket volume, and fork travel.
            I don't know what it is either, and don't think it's worth doing in this discussion.
            My point is; pressure increases as the fork is compressed, and that internal pressure adds to the force of the spring.
             The smaller the air pocket, the quicker that change occurs.

As far as testing, {back in my dirt bike days} we adjusted fluid levels and found a difference in handling.
 We then got interested in the idea and (using the same viscosity fluid) changed only the level to do a test.
We changed the level, rode the bike to see difference in handling, and measured fork compression with a "set" weight.
Then we changed the level and did it again, and again, etc...   It did make a difference.

That said: I realize the dirt bike had 12" of travel and the Connie has way less {maybe 5"?) so the effect is less.

Ride safe, Ted

PS: I follow you on your hypothetical.
         (Would make only a slight difference, there would be  less trapped air {actual pressure} in the tube).
« Last Edit: July 24, 2017, 04:51:01 pm by connie_rider »
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Offline Steve in Sunny Fla

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Re: Fork leak when bike is sitting
« Reply #21 on: July 24, 2017, 01:23:58 am »
 Sorry, Ted's right, the air column is a compressible gas that acts as a second "spring".  That's the exact reason oil heights can be changed and why they're changed, it changes the air column and makes it more resistant to further compression.

 I found this out the hard way.

  When I first installed the sonic springs in Shoodaben, I misunderstood the oil level setting and set it up with 150mm air gap with the forks extended, not compressed, as it should have been. With that high of an oil level the forks had almost no ability to compress, and the ride was terrible. At that point I had to research what I had done wrong, and that's how I learned about the relationship of oil height in fork tuning.

  to further drive the point home, the early air assist forks actually prove the point. Raising the air pressure raises the forks resistance to compression. why? because the air is compressed. Same thing that happens when the trapped air column is compressed . MOB, I'm sure you know the formula, but iirc compressing the column to 1/2 it's original volume yields the pressure squared, so the pressure spike is considerably more than linear as compared to the compression applied.

  Steve
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Offline connie_rider

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Re: Fork leak when bike is sitting
« Reply #22 on: July 24, 2017, 01:52:52 am »
Thanks Steve. You explained my thoughts better than I did..
I'll admit, I didn't know that calculation.

To add to the confusion, I'll throw this out.
  * The I.D. of the C-10 lower Fork Tube is larger than the I.D. of the upper fork tube.
       So when the fork compresses, the fluid level has to fill a smaller area.
       Result; Fluid level rises faster than the amount of travel.
  * The material of the upper fork tube moves into the lower tube, and displaces oil as the fork compresses.
       This displaces additional oil and makes the fluid level rise faster...
  * The compressing spring moves under the fluid as the oil level rises and displaces fluid too.
       This displaces additional oil and makes the fluid level rise even faster...

I think this means (approx.): 5" of fork travel may result in as much as 7"- 8" of fluid level change.

Ride safe, Ted

PS:  :offtopic:
        Sorry about that DC.
          Getting back to the topic.   
             You have to fix your leak..
« Last Edit: July 24, 2017, 04:52:20 pm by connie_rider »
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Offline alan

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Re: Fork leak when bike is sitting
« Reply #23 on: July 24, 2017, 05:54:03 am »
I'm still liking the idea of a springer front end....     :lol_hitting:     :beta:
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Re: Fork leak when bike is sitting
« Reply #24 on: July 24, 2017, 07:45:36 pm »
Sorry, Ted's right, the air column is a compressible gas... Raising the air pressure raises the forks resistance to compression. why? because the air is compressed. Same thing that happens when the trapped air column is compressed . MOB, I'm sure you know the formula, but iirc compressing the column to 1/2 it's original volume yields the pressure squared, so the pressure spike is considerably more than linear as compared to the compression applied.

  Steve


https://en.m.wikipedia.org/wiki/Boyle%27s_law

Not quite...

Its a constant...

And the example of your oil level and sonic springs episode, just shows you can't compress a liquid unless there is an airspace...
Which threr was not, at 150 mm, minus the threaded cap depth of about 20 mm, and compressing the forks 140 mm whwhich is what they can compress...
Well, we know about hydrolock...

Using Boyles law, and all other misconceptions aside, not factoring anything,  IF the forks had a positive pressure of 1 psi (which they do not) at extension, compressing them fully still only leads to a 2 psi presure increase... and makes even less difference on a pre 94 bike as the free airspace in those forks is 30% larger in volumn to begin with...
Compare this to the actual compression rate on the installed springs, no matter whose springs you choose, and this increase in air pressure is moot. Sorry.

Now, when you do begin this whole calculation thing, using an already pressurized sealed cell, yes... it will contribute, but only when there is a physical addition of measurable pressure added prior.

Don't get me wrong Steve, I'm not trying to argue, but I am enjoying this discussion, and it makes me do calculations, and keep my mind from going to Jelly...

(Kinda like Ted's.... layoff the moonshine bro...  :rotflmao: :rotflmao:)

« Last Edit: July 24, 2017, 07:48:51 pm by MAN OF BLUES »

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