Ducati.ms - The Ultimate Ducati Forum banner
  • Hey Everyone! Enter your bike HERE to be a part of this months Bike of the Month Challenge!
1 - 20 of 41 Posts

·
Registered
Joined
·
235 Posts
Discussion Starter · #1 ·
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!
 

·
Registered
Joined
·
1,174 Posts
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-spring-compressor-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.
 

·
Registered
1994 900SS CR, 2002 998 Trackbike
Joined
·
328 Posts
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.
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #4 ·
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.

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...

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!

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!
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #5 ·
...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!!
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #6 ·
this tool will make the job mucho easier when compressing the fork spring to remove the upper dampner;
https://traxxion.com/product/fork-spring-compressor-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... :crying:

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.:wink2:
 

Attachments

·
Registered
Joined
·
235 Posts
Discussion Starter · #7 ·
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!
:wink2:
 

·
Premium Member
Joined
·
731 Posts
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:

 

·
Registered
Joined
·
3,653 Posts
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.
 

·
Registered
Joined
·
3,653 Posts
you can pull the compression adjuster out too, to give the best chance to really lean them. you need a good 12 or 14mm open ended spanner - forget what size they are now - and hold the fork securely. i put them in the vice with plastic jaws. it's too easy to mark them if they're not secure.

make sure the adjuster is in a click, otherwise the little ball pushes the surrounding spring out and you munch it up as it comes out.

make sure the threaded nut insert in the lh fork leg is fully seated too. often people loosen that side and it moves around. offsets the wheel, which then offsets the discs in the calipers. i usually do those pinch bolts to 18nm.
 

·
comrade moderator
Joined
·
27,404 Posts
Thing is, if there's sludge in there, then there is stuff in the shim stacks that needs to come out and complete disassembly is the only way to get that out.
 

·
Registered
Joined
·
7,634 Posts
We can all disagree on what to flush the forks with, but I believe it needs to be done and fork oil is not going to get the job done. Just make sure you get whatever you use back out.
 

·
Registered
Joined
·
3,653 Posts
Thing is, if there's sludge in there, then there is stuff in the shim stacks that needs to come out and complete disassembly is the only way to get that out.
it's not like you can get into the showa shim stack without drilling out the pressed dimples to remove them though. putting the bottom of the cartridge in a tub of cleaning fluid and pumping it up and down is not much different to putting the cleaning fluid in the fork and doing the pump imo. i don't see a lot of benefit removing the cartridges from these forks just for cleaning.
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #16 ·
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:

Okay, that's what we call "petroleum" in Dutch.
Thanks!
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #17 ·
We can all disagree on what to flush the forks with, but I believe it needs to be done and fork oil is not going to get the job done. Just make sure you get whatever you use back out.
I also do not think that clean fork oil will get the job done.
I'm going to use kerosine (petroleum in Dutch) because I've used that to clean all kinds of things and it's not corrosive to metal or rubber parts.

I'll get back to this once I flushed the fork.
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #18 · (Edited)
Update (tips and tricks for first-time oil seal changers);

Flushed the fork with some kerosine, the inside of the fork was pretty clean. Flushed it twice with 150ml kerosine, let it dry next to an electric heater overnight and flushed it again with 150ml fresh fork oil. No problems occurred.

Some things I noticed and didn't read anywhere prior to the install but may be useful for future visitors, looking for info on oil seal change:

1) If you're trying to get the top cap of the fork loose when the fork is still in the bike make sure you loosen the top clamp! This clamp pinches the fork right at the spot were the thread of the cap is. The cap wouldn't come off and I almost wrecked it. Then I loosened the top clamp and it came of with just a little force.

2) I followed the workshop manual for the amount of oil needed for one leg. The manual states 26,84cu.in. (=440ml) per leg and 108mm from the oil to the top of the outer leg (fully collapsed).
The density of the oil I used is 860grams per liter. So 440ml is 378 gr. I placed the oil can on a kitchen scale, set it to zero and put oil in the forks till the scale reached -378gr. I pumped the damper rod like a 100 times, let the fork alone for at least two hours and measured the oil height.
I measured 90mm. Too much oil... Got a plastic tube and removed oil till I reached the required 108mm.
Not sure where this difference comes from. Maybe the 440ml in the manual isn't correct, maybe the 108mm isn't correct, maybe the density of the oil was not correct (although supplied by the manufacturer) or maybe (let's hope not!) something is wrong with my forks...
Anyway; when filling the fork, just measure the oil level. Don't trust anything else.

3) Put a 30cm length of plastic tube (8mm) over the top (threaded section) of the damper rod prior to install. This way you can easily pull the rod up when you're compressing the spring and the tube prevents oil to spil out of the top of the rod when pulling the rod up. The tube catches the spill and allows the oil to flow back into the rod when the rod is pulled up al the way. It's even a good idea to use that plastic tube when pumping the rod after refilling with oil. Pull to hard and the oil squirts out like crazy (and you're 108mm measurement is not correct anymore when the oil squirts out of the fork).

4) Make sure you've got enough rags. Then find some more rags. Then, and only then, start pulling your fork apart. My god, what a mess.... :wink2:


So happy I tried this for the very first time. Not the easiest of jobs but with some very much appreciated help I got great results. Big thx everyone!! Much more rewarding and instructive then dropping your bike at the dealer. And cheaper.
 

·
Registered
Joined
·
3,653 Posts
1/ yep, fielded that phone call before.

2/ oil level is the only definitive measurement you can make.

3/ i have a factory tool that is a tube with an internal thread that screws on to the cartridge rod thread. the central hole used to go all the way through, but i blocked it and drilled a couple of holes in the sides above the thread and below the blockage. you use it to pull the rod up (and push down), and if you lift the outer to cover the range of travel, the oil sprays out the holes in the side and stays in the fork tube. mess reduction achieved.

4/ yep. but you get better at that.
 
1 - 20 of 41 Posts
Top