Hi all,

does anyone know the origins of the two piece springs fitted to my bike.

I have progressive units on order from motorworks.

Bob

pretty standard stuff

lots of reasons for 2 springs instead of one

good luck with the new stuff . fitting similar soon on the project bike .

Thanks Charlie

I looked on the OEM catalogue but could only see single piece springs .

Cannot wait to try the new springs, getting very fed up with excessive front end diving....

Bob

audibob wrote:I looked on the OEM catalogue but could only see single piece springs .

The early RS models had sport forks with similar assemblies. This diagram is from the MAX BMW fiche.

'S' forks or sport forks were a dealer-installed option for K100 and other K75 from about '87 onward, marked by an S stamped and visible on the top plug in the end of the fork tube. They came as standard equipment on the K75S after a two years of production. I fit them to my '87 RS and they are quite firm.

These springs are not particularly effective in non-'S' forks. Notice in the provided photo how a suitably long piece of PVC was used for preload, because they are far too short to do any good. They likely would not produce excessive dive. I would research just what brand forks are on this bike and re-fill them with the prescribed viscosity and level of fork oil. Too little can produce a sloppy action. Too much can be harsh. Look at the inside of each fork leg for marks indicating a brand, like F&S, etc.

A picture is worth many (don't know about a thousand) words.

Here is the OEM spacer & spring arrangement from "S" forks that TWB spoke of in his post. From my K75.

k

I cannot see any "S" markings, and they are brembo forks.


My two piece spring set differs from the set in your foto Gaz.

Just as luck would have it, I found one dust cover cracked when I wiped off the crap, ah well time for new seals 

and covers...

Bob

Sorry for the double post. 

I googled the numbers on my forks, and they are from the k100RS

The guide ring, part number 31421450517 seems a loose fit on the piston is this normal ?

This is my first time I have done fork springs etc, so I want to get it right first time.

Bob

This is where you find the "S" on the so called sport forks.

No "S" marking on my forks Gaz..

There must have been a reason to someone when they fitted the sports springs.

They are not going back in, so they will go in my spares bin, just in case I ever decide to 

buy a bag of bits.....

Bob

I am finding it difficult to compress the new springs enough to fit the circlip.

My current springs sit a lot lower in the leg with retainers fitted and the spacer in situ,  making the circlip  very 

easy to fit.

My current springs and spacer measure 51cm with the spring retainers fitted.

The new progressive springs measure 53.3 , without the retainers fitted, 

so with them fitted , they sit  a lot higher , making it almost impossible

to fit the circlip

OEM part number 31421450539 shows the K100 lt spring retainers, which look

thinner at the base than mine .

Has anyone fitted progressive springs from motorworks and used the original 

retainers, and still found it easy to compress the spring and fit the circlip ?

The only place I can find the retainers are on ebay in germany

bob

Doh...

If I had looked harder, I would have found the retainers  on motorworks.

Hope I can get that circlip in now.

Bob

What a difference to how the bike handles with new springs  ( progressive from Motorworks ).

As per previous posts about fitting them  I did not use the retainers .

I also found out why she used to wander sometimes when leaning around a left hand bend.

The left fork had very little oil in it,  the right fork was okay.

No obvious signs of a leak...  perhaps I forget to refill it after changing the seals ....

Doh...

Admittedly I have not serviced the forks for three years,  lesson learnt. 

The firmer action under braking is nicer, I will fit a tie wrap on the legs, and measure the fork travel.

Bob