brake cam o-rings
 

I have an 82 G/S, recently oil has been leaking
on to the rear brake pads via the brake cam,I
have removed the brake cam and it only has two
o-rings on it, but six grooves on the cam.A friend told me it should have four o-rings,if so which grooves should I use for the o-rings.

Thanks.

As many as you can get in...

And grease well.

and don't forget to renew the felt on the outside as well.

I should have known to ask here first. Just posted on UkGsers about leaking rear brake cam.
So I will ask my other question here too.
What's the best way to replace leaking pushrod tube seals?
I am assuming I will have to replace the cylinder base gaskets and head gaskets also when I pull the cylinders off, or is it possible to remove the cyl without taking the head off?
There is not much info in Haynes or Clymer about this.
Any tips or tricks? Thanks, Peter

It is pretty straight forward:
you will need to take the heads off (bolts run throught the heads to the block). As such, you will need a head gasket and the three o-rings for the cylinder base seal (2 small one Large, you should be able to get this all as a kit) for each side. Check your rocker cover gasket, if they are old they often rip on removal, I like to have at least one spare on hand.

The push rod seals are pretty easy but if you are replacing the push rod tubes as well then you have to take care to seat them properly, but not too deep. It is worth measuring the depth of the stock ones before you take them out.

Don't over torque the heads when you put them back on. This will not help in sealing a leak. If you have a leak it is likely that a o-ring has gotten munched as the cylinder slid back on. Last time I did this I used some heavy grease to hole the clyinder base o-ring in it's groove and keep it from catching a lip and getting munched - seemed to work well.

good luck!

Cameron, be especially careful NOT to overtorque the heads. There is a thread on the HUBB about head torque with the correct valuse. UNDERtorquing {b}slightly[/b] - see the thread for numbers - is worthwhile, as even correct torque can strip the threads in the crankcase. Nasty.

------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

On the brake cam thing.

The groves on teh brake cam on my '81 G/S were not there for O rings - I had to have them machined out.

Later on bm placed a tube so that the brake cam shaft did not run in the bevel drive oil. On my K75C this tube measures 15.8mm OD 14.0mm ID 83.5mm length. It is a push fit into the housing - a little heat helps. This may be a better way of removing the leak. However even this has its problems - as th ehousing heats up the differential expansion can lead to leaks - a small bit of silastic is very helpfull to seal between the tube and housing.

Thanks Guys,
You answered all my Questions. For a change I was looking for info BEFORE I pulled everthing apart and mucked something up.
I did know about overtorqing the heads, as out of four overlanding bmw's in Mr Yuts Bangkok shop, mine was the only one without pulled headstuds...
Timo, I have been using silicone valve cover gaskets from Real Gaskets for years now and they work very well. With care they will last forever, they don't leak, and are easy to take off and put back on. Good stuff, but not cheap. Cheers

That's a good tip on the gaskets: I had heard about them years ago, but forgotten! To think of the many gaskets I've mangled since....

simple (but not alwys permanent) fix for leaking pushrod tubes- tap the base toward the engine block with a hammer and bit o wood to reseat em....

Tapingt th epushrod tubes to fix leaks DOES NOT WORK on newer boxers - I know it does not work on my 1980 R80 G/S for example.

Hi

Speaking as one of the four at Yut's, I heartily advocate the use of appropriate torques!

How's your project going Peter?

Sean

Hi Sean,
My project is going slow and cheap (like me).
I rode the poor old G/S all last summer, just adding gas and oil instead of fixing it first. I am such a bad BMW owner...
Just now ordering seals and carb kit for much needed winter maintenance. The front brake project is ongoing ,with new ebc rotor and pads here ,but not installed yet.
Hoping to do some "more" serious testing this summer to see if this is really a going to be a good south america bike...
How are you making out with your bike...?Siebenrock solution perhaps...let us know

Skits, sorry for hijacking your question.
How are you making out with the cam leak?
I will not be getting to mine for a few weeks yet.
Cheers, Peter

Hi Peter

Bad BMW owner? Your R80 was one of the sweetest sounding I've ever heard!

But... Have to confess my poor old girl is still in a right state. I've just bought a house so funds to fix have been scarce over the winter. Still ridable around town if you don't mind the rattles and oily feet - just wouldn't use on a longer tour.

Siebenrock kit sounds good, but what about the need for higher octane fuel? I've found another low mileage 1996 1000cc mystic and am again thinking about a transplant....

Cheers

Sean

Hey Sean, How about the other way?
Will your tank fit the mystic and that great front end should be interchangable too...
Is that mystic higher geared??? you know you like the speed.....Cheers, Peter

Cameron,

Where in YVR are you? I have an R80G/S I've rebuilt and can help you with things if needed.

Kevin

------------------
Kevin

http://www.nohorizons.net

Hi Kevin, I'm in Revelstoke.
I have seen pics of your bike and it looks great.
Thanks for your offer I will keep it in mind.
I am really not sure what I need for the G/S yet...but I will probably manufacture most of it myself.

I finally got around to fixing the rear brake cam leak...
Very simple really.
Drained the final drive oil.
Wheel and brake shoes off.
Removed linkage arm on the other side, and tapped shaft out.
Cleaned everything well.
There are seven grooves in the shaft, only four are for O-rings(they are deeper). Two per side, about a cm apart.
Matched the O-ring size with nitrile(industrial hydraulic) o-rings.
It is very difficult to get the new O-rings over the splined end of the shaft and other rig grooves without tearing them. So I made a tapered "roll-on" jig out of a plastic caulking tube tip and rolled fairly heavy paper around the shaft over the other o-ring grooves. Then rolled each succesive o-ring into it's groove.
Re-assembled and filled oil.
working well so far.
cheers, Peter

Hola Amigos,
I have a 1983R80ST which has the same rear drive as the G/S. Mileage is 175K. My brake cam started to leak at 75K miles so I changed the o-rings. Leaked again at 100K miles and then the interval of the leaking just got shorter. This was a real problen because I have been in Central and S. America since October and half the time I didnt have a rear brake cause it was slimed with oil. I periodicially cleaned the drum and shoes with gas, changed the orings(not so easy to find sometimes) and kept riding. Now I am looking at changing the 2 bushing system I have for the tube system and hope it can be done.
As the bushings and the cam wear, it is impossible to keep the o-ring from wearing out very quickly. At least the oily brake shoes can be easily cleaned. This suprised me but I did it at least 6 times. Maybe the final word hasnt been written yet on this subject. Bill.
Hola Amigos,
Since I wrote this message I have had the course on the bastard o-rings. I rode to Calgary headed for Alaska and had
Bob,s BMW in Jessup, MD ship up two bushings and the tube listed as the correct part numbers for my machine. When they arrived they were not correct as they were too small in OD/ID. I will post the incorrect part numbers I was sent as soon as I can find them. The bushings came from Germany.
I had a stainless steel tube machined to fit my rear drive and brake cam to finially solve the problem. It took some doing but I got it installed correctly and finially no leaks. A $90 Canadian turned into a $450 job and I was bummed. I will not name the shop I used but be careful in Calgary with repairs. If you have leaks fix it right or pay the price I did. Make it a winter project and rebuild the rear drive at the same time and be done with it. Find someone with experience, tools, measuring equipment and parts to get it done right.
I can recommend Anderwerks in Calgary. Dave knows the bike and has parts. I also recommend this man. He is a great machinist and rides a BMW. In Calgary,
Neils Machine Shop
Stainless steel Neil
Tel no.403 275 8098
neil22@telus.net Bill.

[This message has been edited by Bill Shockley (edited 29 June 2005).]

[This message has been edited by Bill Shockley (edited 11 August 2005).]