Replacing the front fork oil seals. Some questions. - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 41 (permalink) Unread Mar 18th, 2019, 8:53 am Thread Starter
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Replacing the front fork oil seals. Some questions.

I've recently ordered a set of SKF KITB-41S oil seals and dust covers for my '97 900SS carbs. Just waiting for them to arrive...

Since I've never replaced these seals myself I have been reading a lot about this job.
Still, some questions remain unanswered.

1) Front wheel removal; do I need to loosen the pinch bolts on the LHS of the fork or not? This guy (www.youtube.com/watch?v=MFpsZlRxlro) does loosen them, this guy (Chris900ssie on this forum, post #4) tells me not to. So, do or don't? And to understand the proces a bit better; why or why not?

2) Now that the wheel is out the proces of replacing the oil seals is clear to me. Just one question here; what's the correct orientation for the SKF seals? I don't want to mount them upside down and for as far as I know, there are no instructions included with the SKF-seals...

3) With the seals replaced I'm ready to put everything back together. Main question here: torque wrench settings. I have a copy of a workshop manual, but...
-front wheel pin set screw; are these the pinch bolt that hold the axle at the bottom of the fork? Workshop manual states 22,6+24,5Nm. Why these two values? Which one should I use?
-the bolts that hold the fork in the yokes (one big one in the top yoke, two in the bottom yoke). How are they referred to in the manual and what torque wrench setting should I use to tighten them?

4) Flushing the fork; is this recommended or not? And if I should flush the fork what fluid should I use? I've read about brake cleaner (do and don't), mineral spirit (do and don't), fork oil (do), kerosene (do and don't)... So the only way that everyone agrees to be safe is to use fresh fork oil but will fresh fork oil loosen the dirt inside the fork?

Thanks for the replies everyone, much appreciated by this self-teaching, novice Ducati mechanic!

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post #2 of 41 (permalink) Unread Mar 18th, 2019, 10:22 am
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some advice/

this tool will make the job mucho easier when compressing the fork spring to remove the upper dampner; https://traxxion.com/product/fork-sp...ompressor-kit/ do use a thin adhesive tape over the fork stanchion bushing groove & lube well so you don't damage the new seal when installing. seal springs face inside,flush with fork oil so the new oil isn't contaminated.be sure to bleed the inner damper tube of air before installing the upper damper & set the oil level to your model specs.when all else fails in finding torque value use the setting for the bolt diameter.and do have plenty of spare rags/shop towels to soakup excess oil.torque setting is value between the 2 figures.
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Last edited by 2004 999s; Mar 18th, 2019 at 10:56 am.
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post #3 of 41 (permalink) Unread Mar 18th, 2019, 10:42 am
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1) don't loosen them. If you do, the threaded Insertthat holds the axle will just spin and the axle won't come out.

2) look at the old seals as they come out and the orientation will be obvious

3) it's the allowable torque range. Chances are your wrench is accurate +/- a few percent anyways so just set it to the middle, 23.5NM or so. Alternate between both bolts while tightening

4) I'd flush them with something not too aggressive. Kerosene or something is fine.

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post #4 of 41 (permalink) Unread Mar 18th, 2019, 1:38 pm Thread Starter
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Quote:
Originally Posted by Lelebebbel View Post
1) don't loosen them. If you do, the threaded Insertthat holds the axle will just spin and the axle won't come out.
Just what I thought. I just tried it and the axle came out without any problems.

Quote:
2) look at the old seals as they come out and the orientation will be obvious
Why didn't I think of that? Obvious indeed...

Quote:
3) it's the allowable torque range. Chances are your wrench is accurate +/- a few percent anyways so just set it to the middle, 23.5NM or so. Alternate between both bolts while tightening
This makes things clear! I'll go for the middle!

Quote:
4) I'd flush them with something not too aggressive. Kerosene or something is fine.
Okay, kerosene is used by others as well. I think I give it a go.
Just in doubt what kerosine really is. In Dutch "kerosine" is airplane fuel and I don't know where I can get that.
I think "kerosine" in English is like "clear petroleum" or so in Dutch. I hope Google can help me with that.


Thanks for the answers!! They've been a great help so far!

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post #5 of 41 (permalink) Unread Mar 18th, 2019, 1:39 pm Thread Starter
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Quote:
Originally Posted by 2004 999s View Post
...do use a thin adhesive tape over the fork stanchion bushing groove & lube well so you don't damage the new seal when installing. seal springs face inside,flush with fork oil so the new oil isn't contaminated.be sure to bleed the inner damper tube of air before installing the upper damper & set the oil level to your model specs.when all else fails in finding torque value use the setting for the bolt diameter.and do have plenty of spare rags/shop towels to soakup excess oil.torque setting is value between the 2 figures.
Thanks for the advice!!

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post #6 of 41 (permalink) Unread Mar 18th, 2019, 1:50 pm Thread Starter
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Quote:
Originally Posted by 2004 999s View Post
this tool will make the job mucho easier when compressing the fork spring to remove the upper dampner; https://traxxion.com/product/fork-sp...ompressor-kit/
I was thinking about buying a tool like that.
But with the advice on removing the front wheel in this topic was so helpful I gave it a go and the forks were out in half an hour.
Since that was so easy I wanted to try disassembling the forks but didn't have the tool...

So I got my ex-woodworker-brain at work and 15 minutes later I made a tool myself.

Needed:
-Piece of hard wood (I used a piece of oak 12,5cmx12,5cm or 5" by 5")
-Two 8mm drill bits.
-Jigsaw

Howto:
-Make a 5cm (2") hole in the middle of the piece of wood
-Drill two 8mm holes from the side of the wood to the hole in the center, go in and out with the drill bit so the hole is just a tiny bit larger than 8mm
-Be happy to have saved €50.
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post #7 of 41 (permalink) Unread Mar 18th, 2019, 1:56 pm Thread Starter
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And to those who noticed: yes, I like working with wood. The paddock stand is also a DIY wooden one...
Works just a good as a 'normal' one.
And it's much more rewarding to make things yourself than to buy them.
Happy days!
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post #8 of 41 (permalink) Unread Mar 18th, 2019, 5:47 pm
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Quote:
Originally Posted by BelgianDuc900SS View Post
Okay, kerosene is used by others as well. I think I give it a go.
Just in doubt what kerosine really is. In Dutch "kerosine" is airplane fuel and I don't know where I can get that.
I think "kerosine" in English is like "clear petroleum" or so in Dutch. I hope Google can help me with that.
Kerosene is a refined version of Diesel fuel. In terms of refinement from lowest to highest: Heating Oil, Diesel, Kerosene, Jet Fuel. The more refined they are the more astringent and volatile and less oily they become. In the Army we use JP8 (jet fuel) in our diesel engines and add a small amount of automatic transmission fluid to return some oil/lubricity to not burn out our fuel pumps. They all smell similar.

Kerosene is used in space heaters that look like this:

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post #9 of 41 (permalink) Unread Mar 18th, 2019, 6:27 pm
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Dont flush them with anything other than clean fork oil.
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post #10 of 41 (permalink) Unread Mar 18th, 2019, 7:02 pm
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if they're clean you could use a light fork oil. but if there's any sign of sludge i usually use white spirit (naptha?) to flush them out. put a few hundred ml in, cap back on, pump it up and down a few times then shake it around a lot. you need a solvent to get the grey sludge out of the bottoms of them. check the bottom of the spring, that's where you'll see any sludge build up on the non sbk forks where the spring sits at the bottom. get in there with something long - i have a nice long piece of narrow aluminium flat that i poke down and run around the cartridge / bottom of the leg to loosen the sludge. or pull the cartridges and clean as required.

then let them hang upside down for a while.

showa generally aren't too bad sludge wise, nothing like ohlins are. although they are pretty old now.

know all wanker
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