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R50/2 rear engine seal

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cderosa202
Posts: 7
Joined: Tue May 18, 2021 6:56 am

R50/2 rear engine seal

Post by cderosa202 »

Hey all.
Simple noob question. I’m going through my Barrington book and I’m ready to install rear engine oil seal. Book says “concave side away from bearing” but it seems like the flat side should be out.
Am I just getting things confused? I don’t have a pic from tear down of it, so I can’t confirm.

Lmk. I am going on the assumption the flat side is out (toward trans). All the other seals are this way.
Thx.

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jwonder
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Re: R50/2 rear engine seal

Post by jwonder »

I just did this last night on my R50S so I am very fresh in the view. Thinks about it this way:

The higher stepped outer side should be towards the rear. Why, because the center will ride on the center of the bearing and the step gives space to clear the outside of the bearing and let oil flow. You will also note that the step also gives area for the wavy washer to ride in. This is why it is important to ensure you have at least .065" clearance between the back of the flywheel and the bearing. Mine measured to .062" and even though I was sure that would be enough, I took .004" off the flywheel anyway just to be certain.

Hope this helps.
James Wonder
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York

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