Just wondering if there is a quick way to check the fork oil?? - Honda RC51 Forum : RC51 Motorcycle Forums
 
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post #1 of 6 (permalink) Old 09-11-2012, 07:58 AM Thread Starter
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Just wondering if there is a quick way to check the fork oil??

I want to check the fork oil levels in my 03 sp2. I was wondering if there was a way I can just pop the tops off the fork tubes without messing up the damper controls or do I have to disassemble the whole control system just to check it? Also I was wonder if there was any "easy" way to drain then and swap in some fresh fluid without removing them from the bike. I mean I guess a syphon pump would work but I would rather not use one if possible. Like possibly if you take off the lower adjuster, will the fork oil drain from the bottom?? Any help would be greatly appreciated!
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post #2 of 6 (permalink) Old 09-11-2012, 09:59 AM
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One of the reasons why a fork is partially disassembled is so all the old oil can be purged from the cartridge and also the surrounding area.
With the fork cap and spring removed, the cartridge can be worked like a churn to pump all the oil out of it.
Without doing that, you will always have a quantity of contaminated oil inside.

Also, since a certain quantity of oil remains, you can't be sure you're adding the correct amount of oil back, and with the spring installed, your level is unknown as well, so the air space is also inaccurate.

The main reason fork oil is replaced is due to fine metal particles that are shaved off the fork tube wall when the spring bows and rubs against it.
The metal particles eventually settle at the bottom of the fork and accumulate around the compression valve.
Not only do they interfere with valve shim operation, they can (if bad enough) get impacted into the valve orifices.

There have been reports of old bikes that have never, ever had their fork oil replaced, and the metal particles had completed blocked the compression valves to the extent the valves had to be replaced.
The particles had been pounded into the valve orifices to where they couldn't be chiseled out without destroying the valves themselves.

Since the RC51 has and attached compression valve assembly rather than an internal one on most forks, it is possible to remove the valve assembly and possibly drain the oil.
There are two small O-rings for each assembly. Don't lose them as Honda doesn't sell them.
Then you can pump the fork to push the oil out from the cartridge and fork area.
If you try this, I suggest placing the fork in some kind of pan or such as it will be real messy.

Then you can reattach the compression valve assembly, and then unscrew the fork cap and add the prescribed quantity of oil, then pump the fork to try and work the oil back into the cartridge.
You will have to pump a while then let sit for 5 minutes, then pump again, several times.
There will be no way to know if the air space is accurate, but it will be quick and dirty.

Last edited by SubSailor; 09-11-2012 at 10:06 AM.
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post #3 of 6 (permalink) Old 09-11-2012, 11:16 AM
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interesting

Good reading on that one Mr.Sub, That was always my understanding on why you just pull the tubes and pull the cartridge's then give it all a nice cleaning, check springs out and change any bad/leaking seals or all the seals if your like me and like to those things when it is apart. I did not know Honda does not sell those o-rings so mental note made
Seems to me you would have the same amount of time spent doing it right, as oppose to having a real messy and long clean up situation and risk of " metal particles " floating around.

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Last edited by Duckhunter; 09-11-2012 at 11:17 AM. Reason: spelling champ
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post #4 of 6 (permalink) Old 09-11-2012, 07:25 PM
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Quote:
Originally Posted by SubSailor View Post
they can (if bad enough) get impacted into the valve orifices.
I hate that when my orifice gets impacted...

Nice write up Sub



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post #5 of 6 (permalink) Old 09-11-2012, 08:54 PM
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Here's an example of old fork oil.
The gray is metal particles that I mentioned.
This is from a set of Ohlins FG832 forks I bought a few years ago.
Good thing I disassembled the forks and cleaned them out.
I have no idea how old that oil was. It smelled pretty bad too.


Last edited by SubSailor; 09-11-2012 at 10:33 PM.
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post #6 of 6 (permalink) Old 09-12-2012, 05:46 PM
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One of the first things I change on a bike is fluids including the fork oil!...and this is why.



The very first schoolbook that was written had God all over it. --Dave Mustaine
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