question about draining fork oil

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I changed my fork oil today and one of the seals has failed miserably during the process. It didn't seem to be leaking when I took it off the bike, the slider was dry. In the process of draining the oil out the top of the fork I got a bit on the slider, and then noticed while pumping it that I was accumulating a fair amount of oil on the slider with each pump. So now that I think of it, the problem may have been the seal was already bad, and inverting it to pump it was allowing oil to bypass the seal and get on the slider.

I'm thinking next time I'll use the bleeder screw on the bottom to keep the slider as dry as possible during the pumping process. I used to do it that way years ago, and made a special container out of a 2.5 gal water jug that I cut, but I threw it out a few years back because it got old and brittle.

So this got me to thinking, is it OK to get a little oil on the slider while pumping out the old oil, as long as you clean it all up afterwards? Or will that oil have negative effects on the seal?
 
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The seal is designed to keep dirt out and oil in, so I cannot imagine that fork oil would have a deleterious effect on the seal. And, fork oil is not corrosive or otherwise nasty.
 
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dwalby
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The seal is designed to keep dirt out and oil in, so I cannot imagine that fork oil would have a deleterious effect on the seal. And, fork oil is not corrosive or otherwise nasty.
yeah, but on the other side of that coin, you don't generally put a new gasket on an oily surface and expect it to seal properly. The bottom of the seal is always exposed to oil, but the top isn't, so I was wondering if having oil on the top and bottom could compromise the seal. My memory is that I've never been particularly careful about keeping the slider oil free in the past, and it hasn't had any negative effect before, but I thought I'd ask around and see what others think.
 
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yeah, but on the other side of that coin, you don't generally put a new gasket on an oily surface and expect it to seal properly.

For me, the operating difference here is a 'seal' as in oil seal, fork seal, or grease seal, vs a gasket which is usually installed on a dry or gluey surface (surface sprayed with a sealant such as Permatex) that is intended to keep usually oil inside the engine.

That's not what I have done in the past. Whether its a grease seal on a brake rotor (car) or an oil seal, I always smear some of the adjacent lube on the shaft before inserting it to be sure there is a small film of lubrication on the seal. Then after assembling things, I wipe excess oil/grease off the shaft (and exposed part of the seal) and move on to the next step.

Yes, I install gaskets the way you said - dry or with some sealant to prep the mating surfaces but before I apply the sealant, all surfaces are free of grease and oil.
 
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I had a similar thing happen; oil will happily accumulate in the top of the fork recess where the circlip lives, and then appear on the stanchion when you pump the fork up and down. I did remove the oil (using a rag stuffed into the recess, after lifting the dust seal clear) and 2000 km down the road, there's no sign of any problem. The main oil seal won't be affected by the oil, but it does take longer to clear than you would think.
 
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OK, so the responses so far are more or less consistent with what I thought from my past experience, getting some oil on the slider side of the seal isn't really a big deal. So I guess the seal was marginal, but somehow keeping the oil down off the slider in normal riding. Funny how it leaks like a sieve now after just changing the oil, its literally pouring out the top of the seal. I was ready for a bushing R&R anyway, so I'll get new seals/bushings, and clean everything up.
 
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Juts to be clear, at the top of your forks you have two types of seal, the dust seal (which is on the outside of the slider) and the oil seal (which is buried under the circlip). The dust seal won't stop oil or water leaking past, but will keep solid debris out of the circlip/oil seal area. You can prise the dust seal up off the fork leg (sharp screwdriver) and you'll be able to see the circlip and top of the oil seal. If the oil seal is leaking, then that is a whole other story and replacement is needed.
 
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dwalby
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yep, done it dozens of times on various bikes over the years, familiar with both seals, and never saw anything like this before. I pulled the dust seal to see what was going on, and cleaned all the oil off the top of the oil seal. Just turning the fork sideways so the oil had the force of gravity on the seal, it was literally pouring past the seal (maybe a little pumping as well, don't recall exactly). When I pulled the fork off the bike, the slider was dry, go figure. I took a fairly good front end hit while riding last week over some rough railroad tracks, so I specifically looked at both sliders before removing them to do the oil change, they were both dry.
 
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Well, this is weird. Since I can't get parts for a few days, I put the forks back on the bike and took it for a 15-20 mile test ride. Its not leaking. Too soon to declare victory just yet, but I may have overthought things when I saw oil in places I didn't expect to see it.
 
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You got some crud or fuzz in the seal that worked its way out. You can get thin plastic seal cleaner tools that are designed to slide under the seals and lift out the offending matter. I made one out of a milk jug. Sounds like you've got cleared out now.
 

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I had a similar thing happen; oil will happily accumulate in the top of the fork recess where the circlip lives, and then appear on the stanchion when you pump the fork up and down. I did remove the oil (using a rag stuffed into the recess, after lifting the dust seal clear) and 2000 km down the road, there's no sign of any problem. The main oil seal won't be affected by the oil, but it does take longer to clear than you would think.
I had the same thing happen when I changed my fork oil and springs a few months ago. There seems to be oil coming out through the seal on the right tube only when it was being pumped sans spring and fully bottomed out. After assembly and cleaning the tube has remained completely dry.
 
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I had the same thing happen when I changed my fork oil and springs a few months ago. There seems to be oil coming out through the seal on the right tube only when it was being pumped sans spring and fully bottomed out. After assembly and cleaning the tube has remained completely dry.
So glad to hear you say this, I thought I was going crazy. It was only the right tube (on a non-ABS), same as your experience. I had way too much spare time that day, so instead of just doing the job as quick as possible, I was examining everything as I went. I had a feeling that I might have been looking too hard for a problem that didn't exist, and that appears to be the case. Still don't understand why the oil flows where it does on that fork, but apparently it's normal if you had the exact same experience.
 
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After my previous post the thought occurred to me that I've changed the fork oil on my ST at least 10 times, so why did I never notice this before, its pretty hard to miss.

The answer: I always filled by volume in the past, and based on recommendations here I decided to fill by level this time.

When I filled by volume, I used a 500ml graduated cylinder, which has 5ml volume markings. Measure, pour, replace cap. Then I'd pump it a few times before putting it back on the bike. With the level method, you have to pump it without the spring many times to get all the air out to get an accurate level measurement. The damping rod fork seems to behave differently with the spring removed, for reasons I still don't understand. Its the first time I'd done it that way, so that's why I never noticed the oil leaking past the seal before.
 

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..... With the level method, you have to pump it without the spring many times to get all the air out to get an accurate level measurement. The damping rod fork seems to behave differently with the spring removed, for reasons I still don't understand. Its the first time I'd done it that way, so that's why I never noticed the oil leaking past the seal before.
Not to flog this topic to death or to drive you crazy but.......... I've noted that in draining forks that you think it's all out, but when I leave both forks upside down overnight and more oil drains and is evident next morning. Also, this last change out had me get the correct level in the right fork and, just due to time of day, I left the tube clamped in a vise overnight to finish up the next AM. Being a little OCD I remeasured the level and it had dropped significantly, so I topped it up to the correct level.

As you mentioned, I think there is an issue with air trapped in the cartridge. Next time I'll make a point of pumping that cartridge more to try and expel all air, then I'll set the level of both forks, leave overnight and recheck them next day before putting the caps back on and reinstalling on the bike. There is a cartridge rod tool made to pump the cartridge and hold it in position so you can compress the spring and slide the retaining collar in place. Maybe someone on the forum has made one and can share the process/parts list.
 
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Being a little OCD I remeasured the level and it had dropped significantly, so I topped it up to the correct level.
Just curious, exactly how much had it dropped?

If I have to let it settle for more than a few minutes to get an accurate level reading, I'm just going back to the volume method next time. Its not like I'm racing in MotoGP with this bike, close is good enough for me.
 
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Its not like I'm racing in MotoGP with this bike, close is good enough for me.
I tend to agree with this approach. As long as we're not talking a drop of 10mm or more then a few mm either way won't make any difference. The air gap over the oil will make the air spring effect more or less progressive, but I doubt you'd be able to tell unless the fork were grossly over or under-filled.

With regard to priming the damper cartridge to expel air, you can tell when all the air is out as the damping force will feel firm and even throughout the whole stroke. When there is air in there still, you will feel a significant drop in resistance as the piston moves up into the air pocket.
 
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... more then a few mm either way won't make any difference...I doubt you'd be able to tell unless the fork were grossly over or under-filled.
I agree with you which leads me to wonder why the specifications call for a tolerance of +/- 2.5cc. That is roughly 0.5%. Given all the other variables such as rider(s) weight, tire inflation/sidewall strength and road surface that Honda has no control over, why call out such a tight tolerance on the fork oil volume? :shrug2:
 
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