Struggling to rebuild forks after seal change

[FBi7]

Hi peeps,

A little advice needed. Just fitted new fork seals. I'm struggling to rebuild the forks. I've got a Haynes manual and am following it religiously.

It says to compress the inner tube into the outer tube to fill with oil. Trouble is when you attach the allen bolt at the bottom that attaches to the damper, the inner and outer tubes are locked in position. You can't then extend the tubes as the manual says. And there's no way I can compress the spring enough to get the top cap back on. There was almost no tension removing the top cap. Any ideas?

Cheers,

Stu

 

[TallPaul_S]

Upside-down or right-way-up forks? What bike?

The only think stopping the inner tube from moving in and out of the lower (outer) fork leg should be the top cap...

 

[wazza300]

when it says to attach the allen bolt at the bottom have you tried attaching it with the fork tube extended and compressed?

other than that idk but plenty folks on here will know more than me

 

[FBi7]

D'oh! GSF650 SA-K8 Bandit. Normal right way up forks.


With the tube extended, there's nothing for the allen bolt to bolt on to, so the tubes have to be compressed to bolt on the the damper.

I was careful and tried to lay out everything in order as I took it apart, but that's obviously gone Pete Tong!

 

[TallPaul_S]

Is there a damper rod that connects through the spring to the top cap? or does the spring sit on it's own and the top can isn't connected to anything?

If your internals look anything like this

Then the bolt at the bottom only attaches the the damper rod with the small (rebound) spring on it, the springs are then loose on top of that. The damper rods go inside the inner tubes, then are bolted to the bottom of the fork leg, the gap between the small rebound spring and the bottom is the fork travel.

 

[FBi7]

Is there a damper rod that connects through the spring to the top cap? or does the spring sit on it's own and the top can isn't connected to anything?

If your internals look anything like this

Then the bolt at the bottom only attaches the the damper rod with the small (rebound) spring on it, the springs are then loose on top of that. The damper rods go inside the inner tubes, then are bolted to the bottom of the fork leg, the gap between the small rebound spring and the bottom is the fork travel.

Hi mate,

My internals are almost identical you your pic. The only thing is I don't recognise the two items that look like sockets above the two allen bolts on the bottom left of the pic.

Yes, seals,bushes etc fitted first. Then I tried to slide everything down the middle.

 

[TallPaul_S]

Those are the cups which the damper rods (above them) sit in at the bottom of the fork leg, so that the damper rod doesn't move about. Yours may be stuck inside in the gunk and old oil.

So you can extend and compress the inner tube without any internals? Then you slide the lower parts in (the damper rod with the small spring), then do up the bolt at the bottom of the leg. The fork inner tube should still move, bit it'll be limited by the damper rod, so instead of extending to so that the bush is resting against the fork seal, it'll stop when it hits the top of the damper rod (or the spring).

If they're not moving when you've bolted in the damper rod, there's an issue there.

 

[FBi7]

Those are the cups which the damper rods (above them) sit in at the bottom of the fork leg, so that the damper rod doesn't move about. Yours may be stuck inside in the gunk and old oil.

Yes, mine a firmly located at the bottom on the inner tubes. Should I try and remove them, or are the fine where they are?

So you can extend and compress the innertube without any internals? Then you slide the lower parts in (the damper rod with the small spring), then do up the bolt at the bottom of the leg. The fork inner tube should still move, bit it'll be limited by the damper rod, so instead of extending to so that the bush is resting against the fork seal, it'll stop when it hits the top of the damper rod (or the spring).

If they're not moving when you've bolted in the damper rod, there's an issue there.

Yes, I can extend and compress the inner tube with no internals fitted. Slide in the damper rod and do up the allen bolts (the inner tube seems to need to be compressed to do this). It's at this point both tubes become locked in situ.

I'm wondering if it's to do with the damper seat/cups being stuck in the end of the inner tube, instead of being separate from the inner tubes. They look quite snug and look like they're meant to be there lol!

 

[TallPaul_S]

Yes, mine a firmly located at the bottom on the inner tubes. Should I try and remove them, or are the fine where they are?



Yes, I can extend and compress the inner tube with no internals fitted. Slide in the damper rod and do up the allen bolts (the inner tube seems to need to be compressed to do this). It's at this point both tubes become locked in situ.

I'm wondering if it's to do with the damper seat/cups being stuck in the end of the inner tube, instead of being separate from the inner tubes. They look quite snug and look like they're meant to be there lol!

Ahh, yes - if the cups are stuck in the bottom of the inner tube, that will be your problem!! They shouldn't be!

As you can see from my picture, they should be completely separate, only the damper rods at the bottom should attach to them.

If you've put the new seals in, you can try attaching the damper rods, then giving the inner tubes a firm yank to try and release them, otherwise you'll need to remove the inner tubes (and the seals) to get to them.

 

[FBi7]

Thanks for you help so far mate. Much appreciated.

Are those cups plastic? Mine are white plastic, but it does look as though there's still something inside the bottom of the inner tube. Are the inside of your cups white plastic?

Cheers again

 

[Dogbreath]

Those are the cups which the damper rods (above them) sit in at the bottom of the fork leg, so that the damper rod doesn't move about.

They are actually hydraulic end stops. When the forks are almost fully compressed these parts rapidly raise the compression damping rate to pretty much infinity which cushions the impact and prevents the forks bottoming out with metal to metal contact. This is why they are tapered.

The problem with them is that once the fork has bottomed out, it's very slow to extend again, and if you bottom them out by hand without the spring fitted it's extremely difficult to pull them apart.

 

[TallPaul_S]

No, mine are metal, but I wouldn't be surprised if they're plastic - Edit see above, they do more than I realised!. There will be some stuff inside the end of the fork inner tube, but that's normal, it's the valving etc to control the oil when the forks are compressed etc.

They are actually hydraulic end stops. When the forks are almost fully compressed these parts rapidly raise the compression damping rate to pretty much infinity which cushions the impact and prevents the forks bottoming out with metal to metal contact. This is why they are tapered.

The problem with them is that once the fork has bottomed out, it's very slow to extend again, and if you bottom them out by hand without the spring fitted it's extremely difficult to pull them apart.

Well you learn something new every day I did wonder how there'd be no metal to metal contact when forks bottom out!

 

[benji182]

This might be helpful. Sorry if not.

 

[FBi7]

Thanks all,

I think I now know where I was going wrong, and the way forward. Unfortunately, I wasn't able to get the white plastic cups out the bottom of the inner tubes without damaging them so I've ordered some replacements that should be here Friday.

Cheers again,

S..