BMW K bikes (Bricks)

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fb35523

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Hi all!

I needed to replace the right front fork oil seal on my 1990 K100RS, so I went ahead and removed the entire leg. After removing the spring, the dust seal and the clip and loosening the allen bolt in the bottom of the leg, I supposed I could just pull the stanchion and the lower leg apart with some force and the seal would follow. No luck. I have REALLY used force, and I just can't imagine that the seal could resist that much force. It hasn't even moved a tiny bit! Looking at videos on the 'net and from previous experience (CB900 and others) I'd say that something else must be stuck somewhere. I can see the internals of the shock (the absorber?) moving if i turn the leg upside down, and it is completely free since the allen bolt is removed. I can even see right through the leg if I look from the top.
Also, after removing the spring, I slid the stanchion up and down to bleed the last fork oil out, and to my surprise, it seemed to get stuck more and more at one point. After that, I somehow got the stanchion free again, but as I mentioned I cannot get it fully back in again. There are some pictures on my web server showing the fork leg, but I cannot post the URL here since I'm a newbie on the forum. The address, however, is du.skulle.se/K100RS/ . The first one (IMGP5519) shows the fork compressed as much as possible, the following two show the stanchion as far out as it goes.


Any thoughts on how to get the seal out (and the stanchion!)? Even more force, or will I ruin the internals of the fork leg?

Any help is greatly appreciated!

/Fredrik

    

Inge K.

Inge K.
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Wrap some tape around the stanchion, use a sharp knife to cut away as much as possible of the inner diameter of the seal and use a screwdriver ( or similar) to wedge it out.

When using to much force by pulling the stanchion and slider apart will possibly destroy the bronze bushings.

Inge K.

    

fb35523

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I can't believe it! I could finally pull the seal out. The bushing beneath it could be persuaded too, but to my dismay, some previous owner seems to have ruined the fork!
du.skulle.se/K100RS/IMGP5535.JPG
I'd say they've tried to get the guide bush (see www [insert dot here...] ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51709&catID=31&catname=31+Front+axle%2c+front+suspension) to be permanently fixed to the slider. Why is that? Some ugly renovation attempt gone bad? It must be the guide bush that stops the rest of the stanchion to get out of the slider.
I guess i need to get the guide bush out of there somehow... Perhaps I'll drill a series of small holes between the bush and the slider. Any other ideas?
/Fredrik

    

RicK G

RicK G
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Before you do any more check the tube for straight it sounds to me like it has been bent and an attempt has been made to straighten it but not quite right and so the thing with the bush.


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Bikes 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

fb35523

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The stanchion is straight as far as I can measure it, and I guess the slider can only be measured when the stanchion is out of there... I have no reason to suspect that there has been an accident with the bike, but you never know. If anybody has an idea as to how to get the guide bush out of the slider, please let me know! I just cant seem to get the stanchion back in, so my only chance is to get it out and fix the problem.

/Fredrik

    

Inge K.

Inge K.
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The slider has a bit wider diameter in the upper part (about half the lenght, don`t remember exactly, a couple of years+ since the last time I open a fork like this).
It could be that the stanchion bushing have been to much abused and on its way out of the groove,
and this is the reason for the stanchion/slider being stuck together.

When disassembling this Marzocchi fork it `s best to remove the sealing ring first (which can be really
thight due to corrosion), and the contact surface between the two bushings is very small and the material
soft (easily squeezed out of shape).

Inge K.

    

fb35523

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Hi!
I let a repair shop disassemble the fork. They really had to force the guide bush out by pulling the stanchion repeatedly with a lot of force (I was obviously too soft for the job...). Two internal bushings were destroyed in the process (or were deformed prior to that), so it cost me another 40 Euro plus 90 for the job. Too bad, but what can you do?
Thanks to all for your suggestions!
/Fredrik

    

walker

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Hi. I have a 1991 K100 RS 4 valve. I have experienced the same problems.

For me it has been the outer bush on the upper tube. The bush spread enough to hook the lower(inner) bush.

I replaced with entires from 93 KLT 1100.

The internals are different. Both have ribbed fronts on the lowers. Bothy are ABS models.

walker

    

Inge K.

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That`s why it`s best to remove the sealing ring before disassembling, these bushings easily hooks together.
And if the sealing ring is mounted you must use even more force to pull the stanchion and slider apart.

From 08/91 the RS 4V fork is identical to the one on the K1100LT.

Inge K.

    

walker

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Inge, In my case the externals are identical as far as I can tell. Internally however, the k100 has ABS side with adjustable dampening and the other has no adjustment. The internals are different from one another on the same bike. The 1100 forks have the dampening feature on both sides. The springs and spacers are the same In length ,diameter and twist. i ended up destroying the lower of the RS ABS side fork to retrieve the stanchion and internals. The stanchion bushing had snaged the lower bush and would not pass to seperate the parts. The seal is no problem to pass if the bushes clear.

    

walker

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Inge , I apologise if it seems I was picking you out for contradiction. I'm just trying to point out some differences that are confusing me here. I also noticed the 1100 has a "valve" at the bottom and the K100 has a screw. These are the ones that hold the internals and two parts together. The upper caps are also different between left & right on the K100. The arrangement of hole patterns are also different in the damper cartridges. I thought this would be a simple job, but has turned into quite a chore. If I can get 3 of these apart, I should be able to match up the parts and make a working set.

    

Inge K.

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This seems a bit strange, according to the part manual a RS 4V should have identical internals in both legs
up to 08/91, when it was changed to the damper cartridges as used on K1100.

Earlier RS 2V models with sport suspension did have different internals left and right, but that was
Fichtel & Sachs and not Marzocchi.

Inge K.

    

walker

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Sorry for long delay before reply. Thank you for this input. I need all I can get on this bike. I believe mine is late 91 model. Also I am at least the 3rd owner so things may have been changed before. I have not found an S on the cap. I only know the forks fitted when I first opened them had damper in one and just spacer in the other. The spacer cap also had a shoulder to catch the top of the spacer (PVC tube)which would not allow the shim (holed disc) to even be installed.

The 2nd set, I installed were 1100 types with dampening in both sides. Both I believe are Showa. I have DL'd the K1100 and Haynes K100 manuals here. The 1100 is more thorough and much closer to my bike. The Haynes is for pre 89 models. Mine has many similarities to pre 89 but different entirely in small details.

walker

    

walker

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zonenfiele has a post with link about 4 posts down. If I read his chart right it shows Showa from 8/91 through the K1100 range.

    

Inge K.

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To me it looks like your 1st set of legs is a mix of old and new types.

You earlier mention adjustable damping in one leg, AFAIK this feature haven`t been available on these K`s
Could be that you also got some non genuine parts in one leg.

About Zonenfeiles link, it shows: Showa 8/91-1996 all K75`s.
Showa 41,0mm ---Marzocchi 41,7mm.

Inge K.

    

walker

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Inge,

I think you are right as to the type and the mix of parts.

I looked again at Zonenfeiles chart and guess I misread it. My copy shows Showa on the K75's as you say but no text in the manufacturer for the K100/1100's. I assumed they were Showa also.

They are 41.7 mm

walker

    

jandalboy

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Hi team.Just had the same problem with my new sight unseen purchase of a 1990 k100rs.Information here is really appreciated thank you all
I put the stanchion in a vice (with good protection around it) and with a broom handle through the axle hole on the slider violently jerked it out til it jammed hard then screwed it off.Took a lot of work to destroy the bush enough to get it out.New bushes and seals fitted and shes all go.

    

jandalboy

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Sorry i should of mentioned i removed the circlip,oilseal and slider bushing first.The stanchion bushing was the culprit.Oddly enough one of the slider bushings was new so the folly of not replacing both bushings is proven.

    

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