Fork Seals

[FERRET]

Ok well this morning i set about the inevitable job of changing the steering head bearings on my 07 x challenge, long gone is the smooth side to side action, only to be replaced by a notchy motion. Thanks Gaz for your thread re this hopefully it will help.

Any way on doing this i have discovered that the fork seals are weeping, standard xc forks, has anyone done this job themselves, is it easy, doable by a fairly competant diy er, do i need special tools etc etc,

Any advice greatly appreciated

 

[Losttheplot]

Ok well this morning i set about the inevitable job of changing the steering head bearings on my 07 x challenge, long gone is the smooth side to side action, only to be replaced by a notchy motion. Thanks Gaz for your thread re this hopefully it will help.

Any way on doing this i have discovered that the fork seals are weeping, standard xc forks, has anyone done this job themselves, is it easy, doable by a fairly competant diy er, do i need special tools etc etc,

Any advice greatly appreciated

It's pretty straight forward, but you will need a special tool to drive the new seal and bush back into the leg (the bush pops out when you pull the fork leg apart).

Loosen the big nut up the top of the leg.
Remove leg from tripple clamps.
Finish unscrewing the big nut on the top of the leg, the outer leg will then part from it, and slide down the leg.
Now you will have the big nut on the top of the fork held onto the damper rod, which is locked in place with a nut on the damper rod. these will need unscrewing against each other, you can then remove the big nut on the top, and the springs, spring seats (nylon "top hats") and also the spring bush (a bit of black plastic tube).

Empty the remaining oil from the fork and then pull the outer leg from the inner.
this will take several good pulls, and it won't part unless you dislodge the bush in the outer leg.

Just be carefull you don't loose the little rods inside the damper rods.

Fit new seals, drive into place with a seal driver, then reassemble in reverse to initial removal.

simple, but messy.

hth

 

[Gaz]

I made a seal driver (yes Timpo!) and it worked fine. You can borrow it if you like. The job overall is straightforward. If you are not too confident I can help you out, I used this video (and it's second part) as a guide, really useful:-

<iframe width="420" height="315" src="http://www.youtube.com/embed/Y43k1qFVGW4" frameborder="0" allowfullscreen></iframe>

 

[rossi]

for anyone who is a complete novice at swapping fork seals.

In addition to the earlier instructions (working from memory, but I have done this job more than once on a number of bikes):

It is easier to loosen the fork cap it you undo the pinch bolts on the upper yoke first as these can compress the outer tube onto the cap.

After removing the fork invert it, prise the dust seal from the bottom (now the top) of the outer tube and remove the circlip that holds the seal in place. A flat bladed srew driver is normally sufficient.

With the fork rwu. To undo the top cap from the top of the damping rod you need to hold the locking nut with a spanner. You either need to push a spanner between the coils of the spring or compress the spring and get the spanner above it. As you compress the spring the damping rod will slide down too: a third hand helps here but I always manage somehow. If you compress the spring quickly you have a fraction of a second to slide the spanner in above it before the rod sinks down too far. Remove spring and invert the fork to pour out the oil. Pump the damper rod to expell the oil.

Briskly fully extend the fork so it acts like a slide hammer and removes the seal.

I have never used tools to remove or refit bushes, other than a flat bladed screw driver to slightly prise open the inner (top) bush in order to remove it.

I cover the end of the inner tube with either a freezer bag or insulating tape to protect the seal from damage caused as the seal is slid over the end and past the bush seat.

refit the inner bush and turn the fork upside down, resting the end on a block of wood to avoid damage to the outer tube. Again a third hand is useful - to hold the fork inner up as it will want to slide down and get in the way.

I don't use a seal driver to install the seal. Cut an old seal in half with a hacksaw. This can be held around the fork to press on the new seal - tap down gently with a mallet, working your way around the seal. It takes a bit of time to get it started as it needs to go in straight. Once the new seal has been tapped down a bit into its seat, remove the 2 halves of the old seal. I then hold the long end of a suitably sized allen key against the fork with the tip resting on the seal. Working around the seal again, tap the other end of the allen key with a mallet to drive the seal home. My usual mechanic uses the same method.

Replace the circlip, pack with a little grease and refit the dust seal.

Turn fork right way up and fill with oil, working the damping rod up and down to expell any air. Oil height (air gap) is measured from the top with the fork fully compressed.

Reassembly from here is the reverse procedure.
Extend the damper rod and drop the spring in. Again you have to compress the spring quickly to get the spanner in above it before the damper rod sinks or push the spanner between the coils. Refit and tighten the fork cap. Slide the fork outer up and screw the cap into the outer.

refit fork, tightening the top cap once the lower pinch bolts have been tightened.

I believe the damper rods in each fork are different - makes sense if you think about the damping adjustment on the forks. It is best to do one fork at a time to avoid swapping parts between forks.

common sense : There are a few different parts in there. Have a clean area to lay them out on in order as you dismantle the fork.

 

[FERRET]

Thanks for the replies, Gaz i may well be in touch

 

[FERRET]

Just one last thought before i embark on changing the fork seals, i use the bike mainly off road, has anyone put progressive fork springs in? does it make a big difference? or would i be better putting the £100 or so towards getting some ktm 640 forks? or just leave as is,

 

[rossi]

I can't comment on the progressive springs but I do like my 43mm WP forks. The damping adjustment actually works and I have been able to get a setting that I like. I did have to replace seals and bushes on the forks and it would be sensible to budget for this. If it is not needed then you have a good excuse to spend the cash No doubt they could be further improved with a full rebuild for my weight by a suspension specialist, but Bas (Hyperpro) agreed that the ktm625 forks which I have are a big improvement over the stock forks.

 

[Gaz]

I put the Hyperpro progressives in mine but haven't actually ridden it yet. But I could feel the difference just by pushing on a free-standing fork. Much less armchair like and you could tell they are non-linear by the increasing rate of change of stiffness.

 

[frostyuk]

been there done that with progressive springs and then the 4357 fork replacement, imho the progressive springs (i went hagon) firm up the front end and stop the fork dive i was getting (am 110Kg in kit) which was for me a big improvement over stock but the 4357 (from a ktm 640 lc4-e and revalved) are in a different class altogether

 

[FERRET]

Thanks for the replies, dilemas, dilemas

 

[mtncrawler]

Thanks!

Gaz/Rossi..and all really,

Thanks for the info and vid links...very timely for myself as well. New owner here - I picked up my X with only 950 miles on the clock and, while waiting for my new shock to arrive, the forks are next. They are definitely original seals/wipers and I'm sure the oil could use a change anyway. Bike came with a set of HP progressives, so I'll throw those in at the same time..

Can't believe what the dealer wants for seals/wipers....so I'm ordering parts from RaceTech at about 1/2 the cost...

PS..just noticed the age of thread..so add a year to that "timely" comment.. Great info regardless of the timing!