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Discussion Starter · #1 ·
Migrated from old forum..

Originally posted by Harry
Fork Seal replacement 101

Tools you will need before you start.

12mm spanner

14mm spanner

6mm allen key

Rearstand and Frontstand preferable (of the headstem variety)

10w or 15w fork oil

Replacement fork seals

Rags rags rags

2 cans of degreaser

**** Thanks have to go to Stealthassasin for loaning me his bike for the project!!! **** he tells me his bike never felt better!!


Take One CBR250RR

Remove allen bolt on front, 3 allen bolts from each side of the nose cone and remove mirrors. Pull front fairings off half way and

then disconnect front indicators

Remove bolt which holds brake lines in place

Undo two 12mm bolts which hold instrument cluster to mainframe

To leave your cibby lookign something like this

Undo 12mm bolts which hold in left and right brake calipers and slide off disk being careful not to chip the paint on your wheel

(you can slide a piece of cloth between the caliper and wheel when sliding off)

Loosen 12mm pinch bolts on left of bike (when looking from the front to the back of the bike)

About now you want to place the bike up on stands. Rearstand is a must, and if you have a frontstand it makes life MUCH easier. I

used PeeDz' stands, so if you need to get in contact with him please click below link


If you dont have a frontstand click below to view Eclipze's "how to prop a bike up from the sump tutorial


Once it's up with no wieght on the front wheel undo main bolt which holds front axle in place

Loosen right hand pinch bolts

Remove front axle and remove wheel leaving the bike looking something like this...

Remove Mudguard (sorry no pic of that!!!)

Loosen Allen Bolts on upper triple clamp to releive pressure on the fork cap

If inserted, remove the two black covers from the tops of the two fork caps

leaving the caps looking as follows

Insert 17mm Allen key took and loosen fork cap

On left fork, undo 12mm bolt which holds in clipon


Undo 14mm bolt on lower triple clamp but hold onto the fork at the same time as it may slide out!!!

On left fork, undo 12mm bolt which holds in clipon

Undo 14mm bolt on lower triple clamp for right fork

In order to remove forks completely a circlip needs to be taken off the forks which can be undone by simply using your nails to

open and slide off fork leg as follows

One both of the circlips have been undone, simply rotate the fork in a clockwise/anticlockwise motion whilst giving it slow

downward pressure until for fork comes out, leaving you with two of the following

Use your 17mm allen key to remove the fork cap [red]*Note there may be a bit of force and the cap may spring up so hold it firmly.

The pressure is not one of those, dont hold the cap and it will hit the international space station type forces, more a oh crap

where'd that f**ker of a cap go.. i know it fell beside me somewhere....[/red]

Once undone you will reveal the spacer, a tube of approximately 15cm in length. pull this out and blow it will be a washer, and

then below that the spring.

Below is the top of the fork spacer tubing

Pour out the oil making sure you catch the spacer and spring.

Once out you will see the following

You can see here the spring, the spring spacer and the washer. Note the colour of the oil which even on this aussie delivered bike

is starting to turn black and sludgy. The oil used SHOULD be a honey colour and not have a horrible odour. For those with grey

imports you will find your oil will actually be black and somewhat mercury like in colour.

Next step is to remove the valving and fork seals. To do this there is an 6mm allen key which holds in the valving unit to the

bottom of the fork as seen in the following two pictures. *this is looking from the bottom of the fork to the top, the axle pinch

bolts will need to be removed here.

The method I have to undo this bolt is to have the fork leg sitting on the ground with one foot on the fork. ie on bended knee with

the fork leg under your front foot. Insert the allen key and use every single piece of energy you have to loosen the masses of

thread locker that has been used here from factory. Be careful of people standing behind you here as you may let out a little

muscle straining fart as you try to undo this bolt. I'm not kidding here when I say this is the hardest bolt you will possibly EVER

have to undo. Once you ear a mighty crack followed by the screaming as you realise you have just skinned your knuckles you can sit

up knowing you have undone the bolt... careful here not to thread the allen bolt.

Once you have applied liberal amount of antiseptic to your hands, you come to the easy part. Pull the fork tube apart and while you

are giving it a bit of outward pressure continue to undo the allen key. If you dont put pressure on the fork leg the allen key will

just turn on itself. You will eventually feel it let go alltogether and you can get the bolt out.

Once you have taken the bolt out you will need to remove the dust cap to reveal the circlip which holds the fork seal in place. If

you look down the staunchion you will see a circlip which holds the fork seal in place.

Use a flathead screwdriver to remove this circlip.

Once the circlip is out, hold the fork lower and staunchion firmly in either hand and pull them apart till it hits the stops. You

will need to use a bit of force here. See pictures below

You will have to do this a number of times and eventually the fork lower and stunchion will come apart leaving you with just the

staunchion looking something like this

Looking at this photo of the staunchion you see the following from left to right. Note the left is the top of the fork leg and the

right is the bottom. First you have the fork seal, then a washer followed by the guide. That's all there is to it.

Pull the old seal off remembering which side of the fork seal is facing up (this is useful when putting on the replacement) and the

washer and guide and this is the time where you degrease the crap out of everything clean it up and let it all dry.

As you can see in the following photo

The staunchion has some light surface rust on it. To get rid of this, use some fine emery paper (im talking 1500 or 2000 grit wet

and dry) and give it a light sanding till the surface rust is gone. If you have bent or chipped staunchions you can buy new ones

for approx $220 at any honda dealership.

Once everything is clean and dry it's time to reassemble. Get your fork lower and staunchion and slide the staunchion back into the

lower. If when you disassemble the forks you see a small thimble like piece of metal, this goes in the bottom of the staunchion

before you slide it into the lower. Once the stanchion is temporarily in place, slide the small spring down the fork tube, followed

by the valving with the pointy side down then screw into place. You may need to temporarily slide the spring and spacer down the

fork to put pressure on the valving as you tighten the allen key.

[red]*** Remember here to use thread locker on the allen key before you screw it in ***[/red]

Also note how tight the allen key was when you took it out. So it may require a bit of force to tighten it aswell!

Once the allen key is tight, you can remove the spacer and spring.

The next part is somewhat tricky. The way I do this probably isn't the correct way but it works for me.

Get some of the new fork oil and wipe it over the fork guide. Slide the fork guide over the staunchion and let it get down into the

lower fork. I now use a flathead screwdriver and hammer to gently tap the fork guide into place as follows.

This may take some time and it's pretty much a case of, a couple of light taps around in circles. The fork guide will slowly slide

into place. Once it is flush in it's spot put the spacer ontop.

Once this is done you have to slide the new fork seal onto the fork stanchion. You have to be VERY careful here not to cut the fork

seal or you have to replace it. The way I do it is as follows. Get some cling wrap and fold it over itself once and then sit it on

the top of the staunchion. Get some new fork oil and wipe some on the fork seal and on the top of the fork and slide it on and down

into place.

[red]*** Make sure you put the fork seal on the correct way here. ***[/red]

You may need to use the old hammer and screwdriver technique here again to get the seal to sit properly. Again light taps and don't

damage the seal. You need to get the seal down enough so that the circlip you took out can sit back in it's seat. Once the circlip

is in, put the dust cap back on, slide the spring in, followed by the washer and followed by the spacer. To end up looking like


Pour in 383ml of your chosen weight of oil. I found the 15w works a treat and is not too stiff.

If you want to do the 20c mod, this is where you would do it. Put 2x 20c pieces on the top of the spacer and put your fork cap on

and tighten.

Before placing the forks back into the bike, put down on the ground and compress a few times to get the oil circulating through the

valving... you will hear air moving through the valves which is normal. This will go away as the air settles and comes to the


Once this is done, slide the forks back into each respective leg and do the removal steps in reverse order to tighten everything

back up.

And there you have it. New fork seals!


Cerby: ive never been to a party where the guys were so comfortable with blow up dolls!
PeeDz: Why.. How many parties have you been to which have had blow up dolls?

· Registered
91 Posts
i had a leaking fork problem.
i used your guide to pull it apart; hence thx, though i don't have any stands.
the thing is apart from degreaser i also used turp to clean my seals and parts coz the seals were leaking a lot.
now i've fixed this problem; does anyeone know whether or not i've seriously damaged any parts esspecially the seals?

also i noticed some ppl say a 20c coin fits in the fork; i've found it seems a bit small and a 50c coin would be a better option.
any objections?


· Registered
522 Posts
thanks for this guide, it helped alot while doing mine.

however one thing did come up in conversation while doing this if your using degreaser to clean everything, doesn't degreaser break down oil? i wouldnt think this would be something you'd want to happen to your fresh new fork oil.

can anyone correct or confirm this?

· Registered
1,002 Posts
crazylegs said:
thanks for this guide, it helped alot while doing mine.

however one thing did come up in conversation while doing this if your using degreaser to clean everything, doesn't degreaser break down oil? i wouldnt think this would be something you'd want to happen to your fresh new fork oil.

can anyone correct or confirm this?

· Registered
463 Posts
crazylegs said:
thanks for this guide, it helped alot while doing mine.

however one thing did come up in conversation while doing this if your using degreaser to clean everything, doesn't degreaser break down oil? i wouldnt think this would be something you'd want to happen to your fresh new fork oil.

can anyone correct or confirm this?
it washes off in water. you wouldn't put it back together while still dripping with degreaser.....

· Registered
107 Posts
Clean using whatever method you want, but finish off with a wipe of carb cleaner or brake cleaner. They remove pretty much everything and evaporate away. The main difference between the two is that brake cleaner leaves nothing behind, carb cleaner might leave some residue, which in the forks would be no big deal (brake rotors are a different story).

Oh yeah, make sure you wear gloves....these products are nasty!

· Registered
4,079 Posts
Reikon said:
^^ actually, nulopn carb cleaner smells rather pleasant!
adn freezes like all fuck when you get it on ya skin

another option is electrical contact cleaner
I notice Nulon have changed their recipe for the Carby Cleaner.

It smells sweeter and less potent, still seems to work fine though.

· Registered
14 Posts
Great tutorial!
Re driving the fork seal in.
Wrap insulating tape on the stanchion (after a spray of brake cleaner and a wipe) above the seal, just enough so it clears the fork tube inner diameter. Use it to slide hammer in the new seal uniformly.
If you wind the last half of the tape on so its below the rest it wont damage the seal at all.

· Registered
5,169 Posts
nappa4eva said:
I'm doing this atm, anyone know if MC22 forks need to be pressurized with air like the workshop manual stipulates (MC17 model forks) ?
So are you doing mc22 or mc17 forks? the mc22 ones don't require any air pressure as far as I know, not sure about the mc17 thou (probably just do what it says in the service manual).

Also, to those of you who still think preload will make your forks stiffer, please realise that unless you have variable rate springs the only thing you are doing is changing your sag. it may feel like the forks are softer because they initially compress more, but that is all that is happening. the stiffness of your forks will only be affected by spring rate (the ammount of force required to compress them a certain distance) and the weight of your oil (this will determine how slowly or quickly they compress/rebound).

Pre-load adjustment

Motorcycle suspensions are designed so that the springs are always under compression, even when fully extended. Pre-load is used to adjust the initial position of the suspension with the weight of the motorcycle and rider acting on it. Both the front forks and the rear shock or shocks can be adjusted for pre-load on most modern motorcycles. The difference between the fully extended length of the suspension and the length compressed by the weight of the motorcycle and rider is called "total sag". Total sag is set to optimize the initial position of the suspension to avoid "bottoming out" or "topping out" under normal riding conditions. "Bottoming out" occurs when the suspension is compressed to the point where it mechanically cannot compress any more. "Topping out" occurs when the suspension extends fully and cannot mechanically extend any more. Increasing pre-load increases the initial force on the spring thereby reducing total sag. Decreasing pre-load decreases the initial force in the spring thereby increasing total sag. Since the weight of the motorcycle and rider are the only forces compressing the suspension from the fully extended position, preload doesn't change the forces on the springs under riding conditions. Changing the pre-load does not change the way the suspension reacts to bumps or dips in the road surface either. Two simple examples using the motorcycle's forks shows why:

1. Suppose that the bike and rider put a total weight on the front suspension of 300 lb. Suppose the spring rate of each fork spring is 50 lb per inch. Installing a 1 inch long spacer in each fork leg gives a pre-load of 50 lb per spring, a total of 100 lb. When the weight of the rider and motorcycle are loaded onto the suspension it will compress 2 inch from full extension (2 inches total sag). Now the force exerted on (and by) each fork spring is 150 lb (1 inch pre-load + 2 inch total sag = 3 inch total spring compression) for a total of 300 lb, balancing the weight of the bike and rider.

2. Suppose we now install a 2 inch long spacer in each fork leg. The pre-load is now 100 lb per spring, a total of 200 lb. The total sag will change since we still have the same 300 lb loading the forks. The total sag will now be 1 inch. The total force on each spring is the same as before, 150 lb on each fork spring for a total of 300 lb force. The front suspension's initial position is 1 inch longer than in the preceding example (1 inch less total sag).

Since the forces are the same in both examples the reaction of the suspension to bumps and dips in the road will be the same. The difference is that there is less chance of topping out in example 1, less chance of bottoming out in example 2. Motorcycle manufacturers generally provide optimal total sag settings. This is also why too-soft springs cannot be "fixed" by adding pre-load, too-stiff springs cannot be "fixed" by reducing pre-load. Changing to springs of the correct spring constant for the total weight of the bike and rider is the only solution. Some motorcycles have externally accessible pre-load adjustments. Typically, this is a screw-type adjustment that moves a backing plate inside the fork against the top of the fork spring. The farther down the adjuster is screwed, the higher the preload. A few motorcycles allow adjustment of pre-load by changing the air pressure inside the forks. Valves at the top of the forks allow air to be added or released from the fork. More air pressure gives more preload, and vice versa. Pre-load on bikes without adjusters can be changed by disassembling the fork and changing the length of the spacer between the top of the fork spring and the fork cap. Spacers can be installed under the rear shock springs similarly. A longer spacer gives higher preload, and vice-versa. The pre-load on both forks should always be the same. Dangerous handling characteristics and possible mechanical damage can result otherwise.
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