Installing New Fork Seals-Using home made seal driver-Guide

[silky666]

Although I did this on a set of Kayaba UD Forks from a Yamaha WR400 ... I figure the basic principles will work on any fork.
Certainly beats paying for it to be done and is a lot easier than it seems at first.

I have made a small video showing the 'hard bit' ... driving the new fork seal into place ... which shows how easy it is using home made tools.
(please excuse the oily hands, grubby fingernails and messy garage):
https://www.youtube.com/watch?v=T-yGhBJYCDk


INSTALLING NEW FORK SEALS ON KAYABA FORKS (YAMAHA WR400)

REMOVING THE FORKS:

Loosen top yoke pinch bolts – Keeping the lower yoke bolts done up – This allows you to easily undo the top cap on the forks.
https://i157.photobucket.com/albums/t69/silky666/Random/removetopcap.jpg

Remove forks from yokes and loosen the top cap on the forks – Do not actually remove the top cap at this point.
https://i157.photobucket.com/albums/t69/silky666/Random/undotocapandremove.jpg


Clean forks thoroughly before taking forks apart – This makes it easier to stop mud and grit getting into the fork internals when they are apart.
https://i157.photobucket.com/albums/t69/silky666/Random/cleanforks.jpg

Remove top fork cap – It will not spring out but hold anyway to stop falling on floor.
https://i157.photobucket.com/albums/t69/silky666/Random/topcapundone.jpg


Extend fork to maximum and pull down on the spring to see the locking nut – Use a spanner or lock grips to hold the nut – And undo the top cap from the fork internals.
This will take a little effort to ‘crack’ the thread – And on mine they then tighten again slightly after 3 turns or so, before undoing fully.
https://i157.photobucket.com/albums/t69/silky666/Random/removetopcapfrominternals.jpg

At this point it is important to note / write down how each part fits together – As you will be cleaning them all later on.
Take off the top cap - Remove inner damping rod – It will slide out as you tip the fork oil out – And remove fork spring.
The rest of the ‘internals’ will remain inside the lower fork.
Pour oil out and dispose – It’s a good idea to let it drain for a while.
https://i157.photobucket.com/albums/t69/silky666/Random/drainoil.jpg


SEPERATING THE FORKS:

Hold to top of fork and the lower leg – And pull sharply apart.
It will feel as if it is catching on something and is unnerving at first – But this is simply the internal bushes/washer hitting the fork seal.
It may take a few good ‘pulls’ – But eventually the fork will come apart.
Note: you cannot break anything here, so give its some effort without worry.
https://i157.photobucket.com/albums/t69/silky666/Random/pullapartfork.jpg


Remove all of the internal bushes and washers from the lower fork leg – And remove the old seal.
Note/Write down the order/ where they go!
Clean everything.


FITTING THE NEW SEAL:

This is the part that causes the most concern and worry.
However, once you have done it once you will do it with ease every time.
The seal is ‘pressure fitted’ and you are meant to use the correct seal driver or take it to a bike shop.
But, there is no need. Follow these simple instructions and its as easy as changing an oil filter ! If I can do it, then anyone can!

Once everything is clean and ready – make sure you have all of your tools at hand. You will need:
a)2 pieces of A4 paper.
b)Sellotape
c)Hammer
d)Seal Driver (Old fork seal cut in half)
e)Seal grease
f)Plastic bag
g)Fork oil


MAKING THE FORK SEAL DRIVER:

Take old fork seal and cut in half.
Make sure that it is slightly less than half of one side (obviously) so that you can easily put it around the fork leg.
The metal in the seal is strong and trying to cut it with metal pliers will simply twist them and take an age.(trust me I tried it). So best to cut through with a good hacksaw.
Make sure that any sharp edges are filed down and the seal driver is clean of filings/grit etc.
https://i157.photobucket.com/albums/t69/silky666/Random/halfsealdriver.jpg


DRIVING THE SEAL INTO PLACE (ALSO SEE VIDEO):

https://www.youtube.com/watch?v=T-yGhBJYCDk

Take the lower fork leg and put the dust seal and spring clip on.
Then push them to the bottom of the fork and tape in place to stop them sliding down and getting in the way.
Take Fork seal and coat inner with seal grease (not just normal grease) or use fork oil.
Note: fork seal goes on open side up.
Place plastic bag over top of fork and gently push new fork seal over fork.
The plastic bag stops the seal getting ‘caught’ and tearing.
Push seal to half way down the fork.
Put on washer and then bushes (coating them in fork oil as you do so).
Take fork upper and coat the seal mating face with seal grease (not normal grease). This is important as it will prevent the seal degrading and also the aluminium of the fork upper corroding.
Take for lower and insert in fork upper.
Gently seat the fork seal into the fork upper -You will notice that it will sit proud.
Make sure the fork is pulled apart ¾ of the way, and wrap the lower fork with the paper, and tape in place.
https://i157.photobucket.com/albums/t69/silky666/Random/paperroundleg.jpg


Now place the fork upside down on a clean and ‘soft’ surface (wood?).
Do not place on concrete as you will be hammering the fork.
Lower the fork leg down until the paper hits the seal and stops it going down further.
https://i157.photobucket.com/albums/t69/silky666/Random/paperhitsseal.jpg


Place home made fork driver against the new seal and gently tap / hammer.
Make sure you rotate it regularly and keep the seal driving down evenly.
Be patient and it will slowly be driven down into the seat.
https://i157.photobucket.com/albums/t69/silky666/Random/tapsealdown.jpg

There are 2 signs the seal is seated properly.
1)You will now see the spring clip recess groove clearly.
2)The seal will start to make a distinct ‘metal tap’ sound as it seats against the metal of the fork upper.
Rough guide is that if you can clearly see the top and bottom of the spring clip recess, then the seal is in.

COMPLETED / NO NEED TO PAY FOR IT TO BE DONE AGAIN:

That’s it . all done.
As you will see in the video – the total time spent actually driving the seal into place is no more than 2 minutes. (Studying the video again and it is actually under 1min 30 seconds per seal)
With the homemade driver, it really is that easy.
Store home made driver for next time (saves you having to hack another seal in half).

Reassemble fork spring, damper rod and top cap / Refill fork with new oil as per instructions in your manual.

FILLING WITH FORK OIL:

Last tip – when setting the fork oil level – use a clean and long cable tie.
Measure the correct depth (from the manual) and mark by cutting a small notch in the cable tie. You can then lower it to the notch and when the oil hits the end of the tie its at the right level (like an oil dipstick in reverse!).
https://i157.photobucket.com/albums/t69/silky666/Random/tieoillevelnotch.jpg

Reassemble the forks as per your manual.
Each fork type needs certain settings of the damping, oil, etc done. Eg: Some forks (Kayaba) require you to loosen off the damper before tightening the top cap.
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There's nothing that shouts "Poor Workmanship" more than wrinkles in the Gaffa tape.

Gaffa tape is like "the force" - it has a light side, a dark side, and it holds the universe together.

[G]

Nice writeup , I’ll add it to the sticky if I remember.

Rather than cutting it in half, in the past I’ve just ground down the outside and inside. The outside is fairly easy with a bench grinder – just push it against the grinder wheel enough that the seal spins fairly slowly with the grinder wheel still spinning fast. Then use a die grinder on the inside while clamped.
As it’s not smaller on the outside and inside, it will easily fall out when the new one is in place.

To drive the seal down I use a cut down plastic drain pipe as a slide hammer. Get a plastic drain pipe at least maybe three times the width of a hand, ideally more.
Cut a slice from the middle so you can squeeze the drain pipe so it’s about the same diamter as your fork. I will then stick some tape around to keep it that diameter.
Ideally you’ll have used a section with a properly flat bottom, in which case you should be able to just drive straight down with a ‘slide hammer’ action (read wanking ), if it’s not properly flat at the bottom, you’ll need to keep turning the fork after each drive to ensure it stays evenly pushed down.

[salty21]

i just used a 2 1/2 inch waste pipe cut down the length, leaving it about 4 inches past the top of the leg then just hit that with a hammer, easy peasy
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04 NSR 125(sold) ---- 03 CBR 600rr(sold) ----90 pan euro ST1100 '' ----02 CG 125
94 CB400 Super Four ---- 2000 VTR SP1 (sold) ---- 08 ninja p8f(sold, meh) ----05 CBR600rr

[silky666]

[Howling Terror]

Not just a pretty face are you.
The Paper around the stantion is a good idea.

Very helpful Mr Silk

Pat
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[.....]

Nice one Silky, guess who will be doing my seals while I drink tea and 'help'?

Still got a decent supply of those caramel bars?

[silky666]

[Vincent]

Your lucky you could pull the fork apart by hand, the last one I did pulled the vice and workbench out of the wall. I ended up having to heat it.
One question - why cut the old seal in half? Couldn't you just slide it over the stantion?
I use a plastic pipe to drive the seal home too, with the old seal in between, that way your driving it home square rather than pushing it one half then the other. You just use your hand to drive it home, (although the suggestion above about having it longer than the stantion so you can use a hammer is a good one). Also, while you have the fork apart, it's a good idea to remove all the internals and clean them well so as to not contaminate the new oil.

Otherwise a good how to

[silky666]

[Vincent]

Even with USD forks, you still have enough room to use a plastic tube, just no hammer. As soon as the bush enters the leg, you can drive it in. I did it this way when I strpped my RGv forks. There's actualy a proper tool to use in place of the plastic tube, it's made out of metal so you can get a bit more weight behind it. The important thing is to drive the seal home square. You put the old seal on first, (upsidedown), then the new one and when you've finshed, just snip the old seal off.

I'm only knit-picking tho

[salty21]

i've never done an upside down one so i retract my earlier comment. yeah good idea
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04 NSR 125(sold) ---- 03 CBR 600rr(sold) ----90 pan euro ST1100 '' ----02 CG 125
94 CB400 Super Four ---- 2000 VTR SP1 (sold) ---- 08 ninja p8f(sold, meh) ----05 CBR600rr

[Blue_SV650S]

Good writeup

... but I do have a couple of comments ....

At the stage just before you 'pop' the old seal out, you don't mention undoing the bottom of the fork - which then allows the fork damper rod bit to come out ...

As a 'best practice' sort of thing, you should also really suggest that one should wind both the damper adjusters right off before disassembling (helps protect the damper needles).
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