Hi Folks,
In his EXCELLENT post

http://k100rt.aforumfree.com/member-s-introduction-f1/greetings-from-the-sunny-isle-of-man-t331.htm#1220

Bonzo commented about having a leak in the rear main oil seal.

Getting the seal replaced is not difficult (relatively speaking) but it is time consuming and daunting when you have never done it before. The collective wisdom of people like Bert and the rest of the group will get you through it without too much pain. The gearbox has to come out and there are a number of tips and tricks that we can impart.

Have you got somewhere you can work on the bike other than under a tarp in the back yard?

So we are all turning the group consciousness onto the exact problem
the first questions to ask are, how do you know it is the rear main
engine oil seal rather than from the gearbox?

How much is it leaking, is it so you need to top up the engine, or is it
a drip every now and then, and how often is that drip happening?

Come back to us on that and we can get down to it. An occasional drip
can be tolerated for a while whereas if it is cascading out it can't.
Regards,
K-BIKE

Thanks for this K-BIKE, Bert & Everyone!

Depending on the difficulty rating, I may very well get a mechanic to do the job. Time (as always) will be a factor for me too.

However, to answer your questions.

I have a garage. There's not much space in there but I can get around the bike.

I can say with some degree of certainty that it is the rear crank seal because of the colour of the oil. Ive only just got the bike and want to service it for piece of mind. My plan was to change the fluids & all filters myself and get a spanner man to do the cam chain. When I noticed the oil leak I took the bellypan off, cleaned the underside of the block and checked the engine & g/box oil.

The G/box oil is lovely & clean & fresh, whereas the engine is looking a tad darker (the same colour as the drip).

It is a very slow drip. So far I havent even had to top up the oil, so it could be that I could wait until winter to do the job - but, in my head, the engine is dripping oil & we dont like that do we?

Wether I do it myself or pay a spanner man, do it now or in the winter, Id welcome any tips.

Thanks all.

Heres the culprit...

Great pictures.

I took some pictures of the seal today but will post something tomorrow.

Bert

Slow drip means it is not urgent but do in reasonably near future. Off to bed now gone 11.00 pm, after a 5.30 am start.
Regards,
K-BIKE

Hi there, i have a questions about this seal. Its leaking at my bike, and i wasnt change it when i took out gearbox to change auxiliary shaft bearings.
So- need to do now-again disassemble all of things
Questions are:
-do i need 250 + degrease of Celsious resistance of sealing ? Or 150 is enough ?
-do i need 'left'(coz output shaft is turning left mostly-am i right ?) seal or both direction be fine ?
-do i need second anti dust thing on seal ?
I found at catalogue that i need to buy size 50x80x10, but at my local dealer they have only 50x80x8 resisted up to +250 deg Celsious with anti dust, left direcion. Maby it will be enough dont push it deep, or push it deep and then bo working on fresh part of flywheel shaft?
Another option is to buy 50x80x10 resisted to 150 deg celsious, both direction - used to automotive.
What you recomend for me ?
Thank You
Crisstof

I would not put anything else than a BMW seal.
BMW had a lot of problems with this seal before they got a good one.
The original seal has already been replaced by a new model.
The BMW # is 11117666186 and the cost is about 20 euros ($28.00).
When you install the new seal, it has to be left out by 1mm.


Bert

Thank you.
I read also somewhere that they change it in the end of '80 - beginin of '90.
So i order genuine BMW part at BMW cars dealer-it is special order, need to wait. Hope it be ok.

Its realy hard to find spare parts, eaven for BMW dealers if you are tellying it is for bike from '85 year Good same number of part had newer models also. Bikes here are not so popular.

Thank You Bert and K-Bike

hi,
I just replaced seal two weeks ago and if I could anyone can (is this english?)
I took plenty of pics and can explain order of things but did not write a proceedure. However I am in process of posting all my sequantial pics with comments.I will gladly help from my limited but recent experience with this proceedure - as it is about time I return some considering all the help i got in forum.
few quick tips:
1) having both clymer AND haynes (as well as Bert's rebuild documentation) is important.
2) in my case the clutch assembly was filthy with oil and I replaced the friction plate as well.
3) tying the central stand to front wheel so it can not fold is a good idea
4) following accident report with central or side stand being suspect i made extar sure mine are in perfect order.
5) i lost my temper while trying to pry seal out but finnaly, lacking a slide hammer found away to do it with a 5kg sledge hammer (it is not as rediculouse as it sounds - OK maybe it is - but it works): http://k100rt.aforumfree.com/engine-and-transmission-f10/any-tips-on-replacing-the-rear-eng-seal-t444.htm#1897


Roy

Well done Roy,
We look forward to seeing your photo essay.
Regards,
K-BIKE

Hi, i just replace this seal.
But im disappointed very much - new seal which i order and received-genuine bmw, have not spring, while mine old one also made by bmw- had it !

Does your seals had spring inside ?

Hope it will be not leaking without it. I think they sold me an old one, hope be enough one.
I made some pictures also,
Need to change clutch plate - its oiled. So when i finish it, ill post pic.

Howdy folks,

An update.

I got a local bike mechanic to do the job for me as he has done many over the years. He gave the bike a major service inc. all fluids, and changed the leaking seal. The faulty seal was well bent, and he said it just dropped out in his hand. It had not been inserted correctly. The new seal wasnt like the one that came out - like Cristoff's (without the spring). The mechanic said he would see how it went and if he needed to he would try to get a seal with a spring in, but it was fine. He was happy with the new seal.

I forgot to bring back the bent seal to photograph and put on the site, I went back to him today and he had thrown it away.

For all the work he charged me £350 GBP - I supplied the service parts. Our local BMW garage quoted £760 labour only - just for the seal replacement!

Now I am happy that it will last for many more miles.