I can't think of anything good about the bearing inner race being moveable on the shaft.
At least it should be easy to stop that.

No, it shouldn't move. I had to use a bearing puller to remove that bearing when I last overhauled a rear drive. I'd get a new bearing and if it still moves, glue it to the shaft using a high-strength bearing sealant. The older Tonti-framed Moto Guzzis have a similar problem with the drive shaft support bearing - the inner race not supposed to rotate on the universal joint but you won't find one that doesn't.

DO NOT buy a cheap no-name Chinese bearing. Buy a Timken or SKF or similar.

The bearing is 25 x 52 x 16.25mm, OEM BMW part number 33 12 1 451 188, but the 'universal' bearing number is 30205. 'J2/Q' might also be a part of the number in some bearing shops.

LifeGuard wrote:
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By the way, if this is your final drive, I would not bother to change bearings according to the scars of a broken tooth it shows...I'd change the whole crown.
Once the crown is broken, even if you remove the pieces, it will crack again, and the missing pieces will unbalance it, quickly destroying the new bearings.

jbt wrote:

LifeGuard wrote:
[/size]

By the way, if this is your final drive, I would not bother to change bearings according to the scars of a broken tooth it shows...I'd change the whole crown.
Once the crown is broken, even if you remove the pieces, it will crack again, and the missing pieces will unbalance it, quickly destroying the new bearings.

Crown is in perfect condition, these marks on the gear are reflections from oil residues 

Two Wheels Better wrote:The bearing is 25 x 52 x 16.25mm, OEM BMW part number 33 12 1 451 188, but the 'universal' bearing number is 30205. 'J2/Q' might also be a part of the number in some bearing shops.

I just ordered a new bearing from SKF, we'll see if that changes the situation

Find a suitable place in the fridge for several hours for the final drive, let it cool down well, then warm up the new bearing's inner race with your wife's hair dryer. She might not mind, but if a question arises, remind her that it's for your health and safety.

Why not add a smear of Loctite?

Jordan53 wrote:Why not add a smear of Loctite?

I will seal it with Loctite 603. I just wanted to make sure that maybe it didn't rotate originally and, for example, it didn't block under the load of the wheel and the weight of the motorcycle. By the way, I ordered a new bearing according to the marking on it, maybe the new one will have a tight fit.