Having found that one of my fork seals was leaking, I removed both fork legs from the bike - 1991 K100RS 16 valve. I have changed the seals and bought a litre of 7.5 oil, but cannot understand what amount to put in each leg. The legs are removed and are draining upside down now. Why do some manuals say that each leg has a different amount of fork oil? As the legs are off the bike should I just put 400cc in each?

*16V*
K1100LT L 350 cc 400 cc
K1100LT R 400 cc 400 cc

K1100RS L 350 cc 400 cc
K1100RS R 400 cc 400 cc

K1, K100RS L 380 cc 400 cc
K1, K100RS R 380 cc 400 cc

From a previous post under 'Fork Oil Level' in the forum. Under BMW's RSD data sheet for your model the left leg takes .34 to .35 litre and the right hand leg gets .39 to .40 litre of 10W fork oil....

7.5W fork oil will give you a slightly 'plusher' ride but may feel underdamped.

(Looking further into the available official technical data it suggests that only K1 models of that vintage would have variable damping and therefore use different levels in each leg...the 16V K100RS should have 400cc or .40 litre in each fork leg.) Bottom line, BMW contadicts itself.

Thanks. I found the same conflicting information too. I chose 7.5 weight oil because I could not find what I should be using and I think the Clymer book said 7.5. I will put 400cc of oil in each leg and see what happens.

7.5 wt is ideal. It won't be under damped but it will ride nice over rough roads.

If the oil has just been drained then .35 in left leg and .4 in right leg because left leg does not drain fully due to the difference in compression and rebound dampers but if the legs have been disassembled and cleaned then .4 in each leg.
I was not sure this was right and when I took each leg apart there was close to 50ml of oil left in the left leg after both had been grained.

I was wondering why as it seemed ridiculous to have more oil in one leg than another...in fact the total amount is exactly the same carrying out a bay service rather than an Overhaul. Thanks for that Rick.

bikerboy wrote:I removed both fork legs from the bike - 1991 K100RS 16 valve.
Why do some manuals say that each leg has a different amount of fork oil?

It was a change of the internal parts in the fork ~mid -91.

Early models should be filled with the same amount of oil in both legs.
Later models have cartridges (same as K1100's) and different amount in each leg.
This is when the legs have been drained through the drain plug, when dismantled
it's the same amount in all legs...400 ml.

To identify, early models 10 mm filler plug...late models 12 mm filler plug.

Thanks for that Inge. I have not stripped the fork legs, but have r3emoved them from the bike. I can confirm that it must be early '91 as it has 10mm filler plugs.
Next think is to order the front brake discs and pads, but at least I know that I need two discs and four pads!

Why do you need new discs? Those seldom wear out.

Themason wrote:Why do you need new discs? Those seldom wear out.

The book say that they are 5mm thick when new and the limit is 4.5mm, mine are less than 4mm thick. The bobbins for the floating discs are also very loose.

The wear limit is 3.5mm if I remember correctly.

is it stamped on the disc?

Saxon7 wrote:The wear limit is 3.5mm if I remember correctly.

That's correct on a 2V model .

Bikerboy got a 4V, which got 1mm thicker discs....and a different wear limit.

Some members like to keep the signature field open...I'll guess the reason is
that they think every member of this forum likes a challenge....like remembering
which model every other member own...........

Inge K. wrote:

Saxon7 wrote:The wear limit is 3.5mm if I remember correctly.

That's correct on a 2V model .

Bikerboy got a 4V, which got 1mm thicker discs....and a different wear limit.

Some members like to keep the signature field open...I'll guess the reason is
that they think every member of this forum likes a challenge....like remembering
which model every other member own...........

Point taken and signature changed. I am not very good at this forum stuff and got the wife to do the signature for me.

I will run the discs as they are for now as I have not yet even ridden the bike. There has been so much work to do on it that I am getting worried that when I take it out on the road for the first time it may turn out to be a bag of nails! When it proves reliable and most things are working then I will spend £117 each and buy two new discs.

Well done , but it seems like it isn't quite correct yet.....your signature shows
only on your last post...it should be visible in all off your posts.

I'll guess you have added your signature under the information tab,
try to add it under the signature tab.

It is under the signature tab, but as you say only shows in the posts since I made it. I prefer the technology of a big hammer than that of a keyboard or some RAM.

It's probably me who remember wrong about this......happens all the time.
Afterall you now got a signature.....