Oil Leak

[jimmyg]

I have a '74 R90 and recently had some oil leaks, so I went in and replaced the rear main seal, oil pump cover w/ new o-ring and trans input shaft seal. I updated the oil pump cover to the latest style with the hex bolts as recommended.

I start the bike up yesterday and there's a fairly solid stream of motor oil running down from that area.

I've done a bunch of these over the years and never had an issue, but my gut tells me it's the oil pump cover. I need to take it all apart again.

[Brickboy]

Agh! Old bikes. Rubbish, eh? My petrol tap has worn out the indents that make that lovely click in all three positions. No spares available but a new tap is at £40.

I'm pondering how much I really like the clicks...

[Jeff in W.C.]

Agh! Old bikes. Rubbish, eh? My petrol tap has worn out the indents that make that lovely click in all three positions. No spares available but a new tap is at £40.

I'm pondering how much I really like the clicks...

It's odd/frustrating that you can buy replacement parts for almost all of the individual parts regarding the Karcoma petcocks with the exception of the main body, the selector/valve [not sure what the official part name is] and those two pieces that make the click and give you the solid feeling where the on/off/reserve are. And, those two thin metal parts get crusty and are hard to clean. I wish they were available to purchase. That being said, if I had to do it again, I'd purchase new petcocks rather than rebuild the existing one. My parts added up to more than half the cost of new ones (excluding cleaners, etc.), and took a while to clean and put back together.

[gspd]

I need to take it all apart again.

You'll surely have to take it apart to fix the leak. yuk!
If the source of the leak isn't obvious once it's apart because there's oil all over the place, clean everything and then put just the flywheel back on and start the bike for a minute without the transmission. Then take the flywheel back off and the source of the leak should be obvious. (With the later lighter flywheel you can actually see right through it when it's spinning.) Contrary to popular myth and many 'expert' recommendations, you do not have to replace the the flywheel bolts every time. I've re-used those bolts many, many times without any issues. Ditto for the driveshaft bolts.
FYI. The rear main seal must be installed bone dry.

[Rob Frankham]

Not even BMW suggest that the flywheel bolts should be replaced but driveshadt bolts are a different matter. The recommendation is quite clear, the bolts are cheap and the results of failure are spectacularly bad. Yes, you will probaby get away with it for a while but I would still replace them. You pays yer money and takes yer choice.

Rob

[Blapper]

Did you fit the seal right way round? Familiarity can breed errors...

[jackonz]

I have a '74 R90 and recently had some oil leaks, so I went in and replaced the rear main seal, oil pump cover w/ new o-ring and trans input shaft seal. I updated the oil pump cover to the latest style with the hex bolts as recommended.

I start the bike up yesterday and there's a fairly solid stream of motor oil running down from that area.

I've done a bunch of these over the years and never had an issue, but my gut tells me it's the oil pump cover. I need to take it all apart again.

I had the same issue with my R80/7 I replaced all that you did and then it leaked again, first thing for me was it engine oil or gearbox oil and mine was engine oil.
The seals I purchased was from a supplier in the UK and having read all I could find on the subject it seems that BMW went through various seals over the years before getting to where we are now, as I had cleaned mine when I first did it i pulled it apart and sprinkled some talcum powder in the area and it was clear it was the rear seal again.
So I took no risks and purchased a genuine BMW rear main seal, now you will need the fitting tool to install it as the seal needs forming and do not put oil on the seal lip at all, also you will need to clean and polish and clean the seal area on the flywheel before installing it and also ensure it is bone dry.

Ive had no more issues since.