If you like our site, please consider joining our club!
By joining you will help ensure that we can continue to provide this service
JOIN HERE!

Master Cylinder Adjuster differences

The place to discuss the R 90 S as well as the R90S Worldnet archives!
rd400f
Posts: 28
Joined: Thu Apr 24, 2014 3:20 am

Master Cylinder Adjuster differences

Post by rd400f »

Hi
My 1974 model seems to have a few differences from what I can see in all the parts diagrams.

Master Cylinder has never had a brake pressure switch...never even threaded for it.
No Brake Switch thread.JPG

The cable adjuster at the master cylinder is weird.

The adjuster at the master cylinder is unthreaded and always has been..
Thread marks on unthreaded adjuster.jpg
It just slides freely in the threaded portion of the master cylinder.
Unused threads in Master Cylinder..jpg
Unthreaded adjuster 1.jpg
Unthreaded adjuster 2.jpg

This leaves the only adjustment for the brake cable this one at the lever.
Brake cable adjuster at lever.jpg
I think that this will work ok I just wonder if anyone has seen this setup before?

Lastly I seem to be missing the Cable End Barrel that fits into the master cylinder clevis.
Missing Cable End Nipple.jpg
Where might I purchase one?
Thanks
Richard

User avatar
srankin
Posts: 1054
Joined: Fri Jul 14, 2017 8:45 pm
Location: Spencerport, NY USA
Been thanked: 14 times

Re: Master Cylinder Adjuster differences

Post by srankin »

Let me ask first, are you the original owner of the bike from new? If not, you may have just found yourself infected with previous owner's disease.

I had two R90S bikes on my work bench for restoration many years ago and I can say, nothing in your pictures makes sense as being BMW set up.

There could be a couple of reasons for this. First, perhaps your bike was an early production bike and there is a very slim chance parts from the /6 earlier bikes were used in assembly. I discount this as the /6 bikes had as far as I know only single disc brakes on the fronts. The master cylinder for single disc brakes versus the dual brakes found on the R90S may be different. I won't say for sure because I haven't taken the time to look up parts on the microfiche.

The other reason for the strange set up could be the previous owner for what ever reason chose to replace or install this system.

I could be very wrong on all counts, if so, forgive me. I have just not seen that kind of set up before on an R90S. Perhaps looking at /6 bike microfiches could help you to figure things out.

Of course there are far more knowledgeable people on the forum who will correct me if I am wrong and perhaps shed some light on what you have. Sorry I can't help more, St.
Owner of a 84, R80RT and 78, R100RS

User avatar
sblaylock
Posts: 189
Joined: Thu Jul 22, 2010 1:05 pm
Location: Victoria, BC. Canada

Re: Master Cylinder Adjuster differences

Post by sblaylock »

Hi Richard,

I'm currently working on a '74 R90/6 i.e. not an "S", but it too has the same setup as what you are showing. A master cylinder without a switch and a non-threading adjustor. I own a '74 R90S and went to have a look, but without taking the tank off I can't see enough of the adjuster to know if it's threaded or not and I can't recall if it has the switch.

Funny, I've had that tank off a bunch of times and never took notice if there was a pressure switch or not.

Anyways, for the R90/6 I just ordered up a Cable Adjuster (32 72 1 234 854), Knurled Nut (32 72 1 232 516) and Feltring (32 72 1 231 610) as the master cylinder is threaded.

Edit: In looking at the pictures you sent, I believe the non-threaded piece is referred to as a sleeve (32 72 1 232 514). In my opinion (setting myself up to be told otherwise) I believe you would only need one adjuster either at the brake handle, which is what you show, or at the master cylinder.

The Nipple Holder should be (32 72 1 230 404) based on the R90/6 I have apart right now.

Hopefully this info helps,
Scott.
Scott Blaylock
Stoney Peak BMW Service
Victoria, BC. Canada
BMW Classic and Vintage Motorcycle Service and Restoration
service@stoneypeak.com

User avatar
wa1nca
Posts: 1213
Joined: Thu Sep 27, 2012 5:15 pm
Location: Ashfield Ma
Has thanked: 6 times
Been thanked: 12 times

Re: Master Cylinder Adjuster differences

Post by wa1nca »

Just looked at microfiches for

R45/N
R45T
R45T/N
R50/5
R60/5
R60/6
R60/7
R65 78-85
R65 85-87
R65GS
R65LS
R75/5
R75/6
R75/7
R80 77-80
R80 85-87
R80G/S
R80GS
R80RT 82-84
R80RT 85-87
R80ST
R90/6
R90S
R100/7T
R100/T
Some breakdowns didn't show a brake master cylinder
The one that did all showed a brake light switch and a threaded adjustor at the master cylinder
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

rd400f
Posts: 28
Joined: Thu Apr 24, 2014 3:20 am

Re: Master Cylinder Adjuster differences

Post by rd400f »

Hi
Thanks for all the info.

I will assume that the bike is what it is and just fit it all back together.

The fact that the parts I seem to have didn't match any parts list I could find was making
me think that I had lost some parts or was mixing parts from the clutch and brakes up.

It doesn't help that I took this bike apart over 30 years ago in a fit of disgust...everything was going wrong
with the bike at the time and I had had enough.

I am surprised that there aren't more missing and unidentified parts in the boxes I have... after 30 years of house moves and shifting around.

Today I even found the missing Master cylinder clevis cable nipple.

There will be even more questions as it slowly comes back together.
Thanks for all you guys info..it helps me from giving up again.

Richard

User avatar
srankin
Posts: 1054
Joined: Fri Jul 14, 2017 8:45 pm
Location: Spencerport, NY USA
Been thanked: 14 times

Re: Master Cylinder Adjuster differences

Post by srankin »

Brook Reams, has done a series of well done videos and write ups on a number of ground up restorations he has done. A couple of them may be of help to you. I know I viewed them last winter when freshening my R80RT and it had not be apart for as long as your bike had, I just have a teflon memory, LOL.

Microfiches can help but can be confusing as heck. Sadly, the Chilton's manuals and such cover so many different models they can be equally confusing at times. I give you credit for carrying on to get the bike together. I had two R90S bikes and time and money saw me sell them off while one was in the crate the other 90% done. St.
https://brook.reams.me
Owner of a 84, R80RT and 78, R100RS

Carott
Posts: 64
Joined: Tue Apr 14, 2015 9:18 am

Re: Master Cylinder Adjuster differences

Post by Carott »

Richard,

I have a 1974 R90S and a 1974 R90/6 with a Ural sidecar.
Both bikes have the /5 style controls on the handlebar perches and they use a mechanical switch at the lever to activate the brake light.
All bikes with an under tank master cylinder should have the unthreaded cable adjuster at the handlebar. The threaded cable aduster should be located at the master cylinder.
It is critical when adjusting the cable for the under tank master cylinder that you observe the depth of the piston entering the master cylinder. If the cable is tightened too much the piston will not return far enough to allow additional brake fluid to refill the line.
Screenshot_20210707-202556_1.jpg
I believe the arrangement was set up this way to prevent owners who were used to cable operated drum brakes from over adjusting the cable and blocking the refill port.
Adding to the confusion is the fact that the handlebar perch for the brake is threaded for a cable adjuster. I believe this is because they used the same part number on the /5 bikes which had a cable operated drum brake.

Brett

User avatar
srankin
Posts: 1054
Joined: Fri Jul 14, 2017 8:45 pm
Location: Spencerport, NY USA
Been thanked: 14 times

Re: Master Cylinder Adjuster differences

Post by srankin »

So it looks like some of the "older" stuff made its way into the new bike. Funny, my 74 R90S bikes had the newer style set up. St.
Owner of a 84, R80RT and 78, R100RS

User avatar
wa1nca
Posts: 1213
Joined: Thu Sep 27, 2012 5:15 pm
Location: Ashfield Ma
Has thanked: 6 times
Been thanked: 12 times

Re: Master Cylinder Adjuster differences

Post by wa1nca »

I bought my 1975 R75/6 from the original owner
It has the cable adjuster on the brake lever with no brake switch
Brake switch must be on master cylinder and most likely also have another cable adjuster on the master cylinder
Its warmer today so ill pull the tank to see if adjuster is threaded or not
Tommy
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

User avatar
wa1nca
Posts: 1213
Joined: Thu Sep 27, 2012 5:15 pm
Location: Ashfield Ma
Has thanked: 6 times
Been thanked: 12 times

Re: Master Cylinder Adjuster differences

Post by wa1nca »

My 1975 R75/6 with single front disc brake assy
Master cylinder has brake switch and threaded cable adjust screw for brake cable
Also cable adjust screw on brake lever

Brett :
Thanks for proper procedure to adjust brake cable on master cylinder
Tommy
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

Post Reply