Bits and bobs > FZS600

HOW TO: Forks Seals, Bushes and Oil

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John Silva:
Originally posted by pointer2null on 07/06/2009


Firstly, this is a guide. I accept no responsibility for any mistakes or omissions. If you break it or injure yourself then that’s your problem.

If you're using this guide to change fork oil, only follow the drain, clean and refill parts of the process.

Tools needed: You will need the usual set of spanners, sockets, Allen keys/sockets, torque wrench, hammer and screwdrivers.

Special tools:
You will need something to drive in the new fork seals. On the occasions I have done this I have used a plastic tube of the right dimensions and a brass pipe fitting that also happened to the correct size. You will need something that will fit over the fork inner without scratching it. The fork inner is approx 41 mm diameters so a plastic tube with an inner diameter of 42mm would suffice. The outer diameter must be small enough to fit into the top of the fork lower. The fork lower internal diameter is approx 53mm so you tube should have an outer diameter of approx 52mm. The tube should be at least 0.5 meters long if possible so you can place it over the upper fork tube and tap it with a hammer to drive the seal in. If it is not long enough you can still use it but you will have to tap around it to drive the seal in evenly.

Parts:
You will definitely need new fork seals and fork oil.
You may need new dust seals (depending on the condition of the old one - if they are ok they can be reused).
You may also need new seal retaining clips if the old ones are corroded - these are not expensive so it may be a good idea to replace them regardless.
Bushes if you intend to replace these as well.


Although this is possible with the front fairing & headlamp assembly in place it is easier to remove it first.

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After removing the fairing etc, remove the front wheel. Take care not to damage the speedo sender unit (1) or loose the inner rotor part. Tie the front calipers (2) to the handlebars so that the brake pipes are not under stress or damaged (2).

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Work on one fork at a time; do not mix components between forks.

Loosen the top clamp bolt on the fork you are working on (1). When this is loose also loosen, but do not remove, the cap bolt on the fork (2). The image below is a MK2 Fazer; the MK1 does not have the preload adjuster.

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A couple of turns is enough.

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Next loosen the lower clamp bolt. In the image below the hex clamp bolt has been completely removed, you only need to loosen it (we removed it for another reason not connected with the fork seals*)

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When this is released the fork will slide down so be prepared to catch it.

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Try and loosen the damper retaining bolt located in the bottom of the fork.

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Sometimes you will be lucky, sometimes you won't. Often it won't loosen because the damper assembly inside the fork is turning. If it won't loosen continue and we will remove it later.

Next the cap bolt can be completely undone.
IT IS UNDER SPRING LOADING SO WILL SHOOT OFF IF YOU ARE NOT CAREFUL!

You will need to keep hold of the top fork tube as when the spring tension is released it will try to slide down into the fork lower - we are not ready for this yet.

Tip out the old fork oil and be prepared to catch (in this order), a solid washer spacer, a hollow tube spacer, a normal washer spacer and finally the spring.

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Note which way the spring comes out - the closer coils are at the top of the fork.

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Here is everything you should have:

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1 Cap bolt (MK1)/preload tensioner(MK2)
2 Solid washer spacer
3 Hollow tube spacer
4 Normal washer spacer
5 Spring

Wipe them off and put them out of the way.

Holding the fork upside down, pump it a few times to remove the last of the oil.

DO NOT LET THE FORK BOTTOM OUT OR IT WILL JAM!

If it does jam then you may be able to release it by pulling it hard, however since you and the fork are probably both covered in oil this isn't easy. If you cannot release the fork, partially refit it into the bike and tighten the lower clamp bolt. Using a piece of wood to prevent damage, tap the fork lower around the dust seal until it unsticks.

If you wish to wash out the fork, now is a good time. We used diesel and I have used paraffin before. Pour a small amount into the fork and pump it a few times then drain. Repeat till you think you've got most of the gunge out. DON'T bottom the fork out! 

Next loosen the damper assembly nut located in the bottom of the fork. If you managed to loosen it earlier this should be quite a simple stage, if not then this is difficult as the damper assembly will most likely rotate in the fork itself.

You will need to find something to put inside the fork to try and jam the damper assembly - a broom handle or a piece of wood with a tapered end works best.

Upend the fork and place it over your pole, force the fork lower down so that the pole grips the parts inside and then try and release the bolt. Be prepared to swear a bit and just keep trying. It took us 15 minutes to release one, and the other just 30 seconds.

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When the bolt is released, slide out the damper assembly.

The images below show you what you are trying to do.

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You should now have all the following bits from inside the fork:

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Next pries off the dust seal to reveal the fork seal and retaining clip

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Depending on how bad the dust seal was there may be a fair amount of gunk in here.

Next pries out the fork seal retaining clip. If you are not planning to replace it, take care not to damage it.

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There are 3 points you can use the get the clip out - the two by the open ends are best if you can identify which they are.

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If the clip is badly damaged or corroded it must be replaced.

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Hold the fork lower in one hand and the fork upper in the other and give it a good yank. This will pull the upper out of the lower and remove the old fork seal.

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1 - upper fork bush
2 - washer
3 - old fork seal

Remove and discard the old seal.

Clean up the fork upper and lower and flush out any gunk.

At this point if you are going to replace the fork bushes, pry off the old ones and fit the new. They are not continuous, but have a split so should come off easily.

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Now take a new seal and rub a small amount of oil around the inner edge. Carefully fit the new seal over the top of the fork. Be careful to get it the right way round. The 'open' side faces inside the fork and the closed side faces outwards.


'Open' side which faces inwards/down

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'Closed' side which faces outwards/up

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Refit the fork inner into the outer. The bush may or may not slip in easily. If it won’t go in all the way don't worry as it will be pushed in when we drive the seal in.

Using you seal driver tool hammer the seal home.

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When the seal is fully seated you will be able to see the retaining clip groove all around the fork lower.

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Refit the retaining ring and the dust seal.

Next refit the damper assembly - make sure the rebound spring does not come off in the process. We found (as in the pics above) that it was easier to insert the damper assembly from below. Insert the retaining bolt and tighten it to the correct torque.

Next refill the fork with the correct amount of fork oil as specified in the manual. The manual specifies 10W fork oil, but many Fazer owners (myself included) use 15W as it makes the front forks less bouncy.

The fork inner must be fully inserted into the fork lower to do this - remember the risk of getting it jammed so DO THIS VERY CAREFULLY!

Fill the fork with slightly less oil than required (440ml instead of 475 as needed). Pump it a few times to remove any air trapped around the damper assembly. Do not pull the fork inner out by more that 130mm or you will cause more air to enter. Leave the fork for about 10 mins to let any air bubbles rise. Measure the air gap and add oil as needed. Keep repeating until you have got the correct air gap.

To get the correct air gap you can either use a rod or micrometer depth gauge and carefully fill the fork until the oil just touches your measuring rod, or you can make up a tool like I did.

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The rigid (bit of old metal brake pipe or hollow car aerial) tube is set to the correct air gap, the fork is slightly overfilled with fork oil and then the tube is inserted. The suction bulb is then used to suck out the excess oil.

When you have the correct amount of oil in the fork, pull the fork inner up (no need to worry about air now) and insert the spring and spacers making sure you get them in the right order. Refit the fork cap bolt- this is a little tricky as you have to depress the fork spring at the same time.

Refit the fork into the bike, making sure the top of the fork is just level with the top of the top yoke, and tighten the lower clamp bolt. Before tightening the top clam bolt, correctly tighten the fork cap nut. Now tighten the top clamp bolt.

Repeat for the second fork.

Refit the front wheel - take extra care to make sure the two lugs on the inner part of the Speedo sender unit are correctly located or they will snap off.

Refit brakes and fairing.

(* The owner of this bike sheared the other so we removed this one to measure it. )  :rollin

John Silva:
Originally posted by limax2 on 20/10/2009


As you point out removing the damper tube screw can sometimes (often!) be frustrating, not aided by loctite being used on assembly. The official Yam tool for the job is a steel spike thing which seems a bit crude. What follows are details of a simple tool I have made that making this part of the job very easy. It can also be used to hold the damper tube when assembling and tightening the screw, as it is easily removed when done.

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These are the bits of the tool.


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This is the tool ready for use.
It is inserted down the fork leg so the slotted end, left in picture, slides into the damper tube. The small nut near the right hand end is then tightened to expand the slotted end and grip the damper tube. The right hand end in the picture is still sticking out of the fork leg and can be gripped in a vice or mole grips and the offending screw undone with great satisfaction and no cursing.  :)
You then back off the small nut and a light tap on the end of the rod (domed nut in picture) releases the grip.

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Tool in damper tube.

If you fancy making one here are some details. All shown in millimetres. The only fairly important dimension is the 18.40 diameter that goes into the damper tube, which has a bore of 18.50 diameter. All the rest can be altered to suit the material available.

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This is the gripping end showing the tapered bit that does the expanding of the slotted tube. The threaded rod is M8, the type you can get from B&Q etc.

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This was made from some tube I had which I think might have been electrical conduit at some time, not sure.
This tube needs to be at least 500mm long so that it protrudes out of the stanchion when inserted into the damper tube. I have welded a large nut on the right hand end, but it's not necessary as a vice or mole grips on the end will do fine.

Of course if you live within striking distance of Chorley in Lancashire you won't need to make one because you can borrow mine.  :)

I made the expander wedge from a piece of mild steel bar, but aluminium etc. or even hard wood would probably do. Instead of threading it it could be fastened to the screwed rod with a nut at the back. The flats on it are not necessary; I just put them there for holding whilst tightening the lock-nut. All very easy on a lathe, but a bit more difficult without one. If you want an expander wedge as per the drawing let me know and I'll send you one, post man permitting!
A couple of thing I forgot to mention.
1) In use don't tighten the top nut too tight because the shallow taper exerts a very strong outward gripping force on the damper tube.
2) The small 1.5mm dia hole at the top end of the damper tube sometimes has a burr on the inside, so best to check that it doesn't end up partly blocking the hole.

snapper:
it might just be me but none of the pictures work
 
its not important at the moment i was looking for future refferance as i have to replace my dust seals soon

Farjo:
Fixed. Thanks snapper :)

Fazerider:
Is there a restriction on the number of pictures a post.. or thread..  can have? 'Cos it looks as though later ones are missing and have been replaced by an error message.

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