Vintage BMW Motorcycle Owners

Hey all. While complete engine rebuild, is it necessary to extract the rear main bearing holder? Don't think it was ever done before by PO's. I can see in drawings that there is a gasket beneath. If so, how do I pull it out? Any special tool needed, or can I go with a regular arm puller? It has what...

Is it possible to pull both off the crank, or is this a job for a engine workshop only?
I want to check if the crank needs a rebuild. If the workshop confirms it as ok, I still would like to exchange that bearing and check / clean the rear slinger.
Thanks in advance for any help.

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Thanks.
I also heard horror stories about the damage modern oils have done to our old engines. Do you have any mistakes or information to teach us?

Someone in the engine oil field gave me a tip to go with MOTORBIKE 4T 10W30 oil.
What do you guys think?

Will 20W-50 oil but with a petrol engine rating - be good?

Oh no.
Now I see what is written on the oil canister: It is mentioned to be used in passenger cars with petrol and/or diesel motors
Well that explains a lot.
And the fact that the used oil was standing for 5 years has nothing to do with this strange phenomena?

I came back to update: I opened the drain plug and was horrified to see what was coming out of there. It wasn't oil. It was a viscous fluid that could barely get out. It had a difficult time to drip out, in heavy long sludge drips. Like honey (or snot, forgive my French). The magnet in the drain plu...

Have a look, maybe it helps you.
Guess the entire depends how confident you are with the state of your engine.

best
Klaus

If so, would it be right to say that our motorcycles can work with any oil available in the market for private diesel cars?
What viscosity?

BTW, I used SONOL oil (local brand) from the Motorex series, with description:

20W-50
API: SF/CD
MIL-L-46152B

Is it ok for my bike?

Thanks.
I will continue with stripping and come back for update.

Found it at the oil pump area. Bike stood for about 4 years, was a good runner before still standing.
Any one has an idea where this sludge came from?