Re - Locating Fork Damper Rod After Fork Seal Replacement

[xbally]

Thanks...but unfortunately the inner surface of the upper part of the damper rod is circular not hex shaped-hence my problem.

I've just shoved a broom handle up into it but first attempts to wind in the allen bolt from the bottom of the fork leg have failed.........

I'm beginning to wonder if I'm missing something here...

[Moto63]

I've just shoved a broom handle up into it

Ooo err…….more tea vicar 😜

[Propellor]

Hi Martin. I assume the screw goes into the female thread just loose on the bench? Just to prove the threads are ok?

It's a long while since I've stripped a fork leg down , but I'm pretty sure I've only ever used a broom handle or similar. I ran a gpz500 for several years but the fork seals never gave issue. Last bike I stripped the fork leg would have been an fzr 1000. I remember it being straightforward but can't recall exactly what I did...   

[xbally]

Hi Andrew.

Yes there's nothing wrong with the threads. They run easily into each other on the bench before trying to re-assemble the forks.

I'm no fork expert. I usually get my mate to do any work like this but I thought I would give it a try as I have more time on my hands.

[themoudie]

Aye Martin,

As you have the the damper rod dismantled out of the fork slider, not still stuck inside the fork slider, now is the time to modify the damper rod.

I would find the point of maximum diameter of the cupped end of the damper rod, measure 1.5mm or 2mm either side and cut a slot using a hacksaw to the 3mm or 4mm width, as per the attached image.

I do not know what the OD of the cup is, but I would then get some steel tubing of a diameter similar to the cup and sufficient length, so that you can grip it, whilst the damper rod is at the bottom of the stanchion. Manufacture a twin pronged key from the tube, to fit in the slot in the cup that you have cut. You could also use a robust, long shanked, wide bladed screwdriver, if you have one?

Suzuki and Marzocchi use this slotted method for retaining the damper rod, rather than hex internal machining of the damper rod cup, as used in the Yamaha forks. I manufactured a key from gas pipe, so that I could dismantle a pair of Hyabusa forks, to renew the seals and bushes.

I have used the broom handle method, but have always found it "iccky" at best, and just bl**dy infruriating in most cases and I have modified them accordingly.

Don't forget a wee dot of nut lock on the hex cap scew when assembling, along with an annealed copper washer beneath it's head, if fitted, as they are on Marzocchi forks.

Hope this helps.

This link to a special tool site may also prove useful to all Thumpeteers:Bikers_tool_box_special_tools

Within the above linked site, there is a selection of tools specifically designed to hold Kawazaki's offending damper rods that you may prefer to purchase, rather than my home work around: Bikers_tool_box_Suspension_tools

Good health, Bill

[Propellor]

Hi Andrew.

Yes there's nothing wrong with the threads. They run easily into each other on the bench before trying to re-assemble the forks.

I'm no fork expert. I usually get my mate to do any work like this but I thought I would give it a try as I have more time on my hands.

Is the problem you're having to do with the damper tube spinning when you try to screw the allen bolt in, or one of locating the respective components?

[xbally]

Thanks for the further inputs Bill and Andrew.

That's certainly a good selection of tools including how to make your own 

Food for thought...........

Andrew as far as I can see the difficulty I've got is twofold : yes the damper rod seems to be spinning AND I seem to have a problem aligning the damper rod and the allen screw.

I'm grateful to Bill for his comments on how tricky this is without the right tools-as my confidence in the workshop (never much) has taken a bit of a bashing with my poor efforts to resolve it.

[Propellor]

Thanks for the further inputs Bill and Andrew.

That's certainly a good selection of tools including how to make your own 

Food for thought...........

Andrew as far as I can see the difficulty I've got is twofold : yes the damper rod seems to be spinning AND I seem to have a problem aligning the damper rod and the allen screw.

I'm grateful to Bill for his comments on how tricky this is without the right tools-as my confidence in the workshop (never much) has taken a bit of a bashing with my poor efforts to resolve it.

Is the Allen bolt a metric course or fine thread?

[iansoady]

They're a great supplier, no minimum order - in fact I'm sometimes a bit embarrassed to pick up a couple of quid's worth - and just round the corener for me so no delivery charges.

[Propellor]

I've no more experience of fork leg strip down than your average home mechanic, so I'm thinking of ways I might approach the issue.

How about putting a length of threaded bar into the thread then assembling the fork, including spring. Remove the threaded bar and see if the pressure of the fork spring force is enough to allow the Allen bolt to tighten up without spinning.

Even if it doesn't quite work, at least the bar is a way of ensuring everything is located, while you wedge in the wooden pole.

[themoudie]

Morning Martin,

As Marvin Gaye and Tammy Terrell said, "It takes two, baby, it takes two, to make a dream come true." 

Well, it might do in your case Martin. If you cannot rigidly hold the damper rod, you will always be chasing the threaded lower end around the larger bore of the fork slider. An extra pair of hands can be very useful.  In my experience a standard/coarse metric thread, or a 1.25mm pitch thread, is used for the bolt holding the damper rod to the fork slider, not the fine metric thread, with a 1mm pitch thread. This may vary from manufacturer to manufacturer, annoyingly Fowlers don't show the size or thread of the cap screw in their parts diagram of the assembly, or the material of the sealing washer beneath the cap screw head. If it is aluminium alloy, I would replace it with an annealed copper washer. Fowlers have no replacement washers in stock and want £3-86 + P&P for one! 

I use a Black & Decker "Workmate", to hold the fork stanchion upright, with the damper rod assembled, oiled, with whatever fork oil/ATF you intend to use (I prefer ATF, as it has a known viscosity, non of the oil weight marketing smoke screen), now is the time to secure the damper rod, with whatever tool you are using and ensure that the threaded end is centralised. Now slide the assembled fork slider, again well lubricated, up the fork stanchion and align the bolt, with its annealed copper/fibre washer, wee dab of nut lock, with the thread in the damper rod, with a wee wiggle and I turn the cap screw in the reverse direction, so that you can feel that it is centralised in the threaded hole of the damper rod, before turning it to tighten. It should be finger tight and I then tighten it up using 9Nm of torque. The cap screw needs to be nipped up, but not have its neck wrung!

Propellor's threaded rod wheeze, is a good idea, to get everything centralised, before removing the rod and threading in the cap screw.

I assume that you have already got this far and you now need to reverse the process in this video?: Kawasaki_GPZ/EX_500_front_forks_strip_down

"If some bu**er put it together, then I can take it apart and re-assemble it too!" 

Good health, Bill

[xbally]

Thank you again Andrew and Bill................

At least this tread is proving to be of a little interest.

I'll take on board all comments and delve further into this.

As I may have said already I have a spare set of forks and robbed the appropriate one and fitted it to the bike after first having re-sprayed the lower so the one I'm working on although the original fitted to the bike will now become my spare.

I'm intending to use the GPZ as my winter transport as the half fairing keeps off some of the windblast.

This was my winter rebuild project from 2023 /2024 which i bought in pieces so was quite a challenge for me to put it all back together with quite a bit of help and advice .

[xbally]

Well something strange is going on here! 🤔
Following up on the advice kindly proferred on here, this morning I tried threading a long piece of threaded bar of the appropriate diameter and it wound easily into the bottom of the damper rod.
I then lined up the broom handle down the stanchion to stop it turning and all was well.
But when I removed the threaded bar and tried using the Allen screw it wasn't long enough to go into the bottom of the damper rod.
This could be because I haven't yet driven in the bush or fork seal which presumably will then allow the whole gubbins to drop further into the leg?
Just really seeking views of people who are more knowledgeable than me before I do anything further!

[Propellor]

Well something strange is going on here! 🤔
Following up on the advice kindly proferred on here, this morning I tried threading a long piece of threaded bar of the appropriate diameter and it wound easily into the bottom of the damper rod.
I then lined up the broom handle down the stanchion to stop it turning and all was well.
But when I removed the threaded bar and tried using the Allen screw it wasn't long enough to go into the bottom of the damper rod.
This could be because I haven't yet driven in the bush or fork seal which presumably will then allow the whole gubbins to drop further into the leg?
Just really seeking views of people who are more knowledgeable than me before I do anything further!

No specific knowledge of the gpz500 forks, but I think there might be a recess in the bottom of the fork leg, for the end of the damper rod to  sit. I wonder if it's not locating?

I assume this same allen bolt is the one that came out initially?

Don't suppose you have a wrecked old fork leg. Could cut a section out to reveal the internal shape. 

[xbally]

Yes the same allen bolt.

No I don't have a wrecked fork leg-only a good spare pair.

Looking further into this Andrew .I've posted on the US  version of the GPZ forum where a lot of UK owners have migrated but no specific answers yet-only reference is to the Yamaha damper rod holding tool.