Large Bolt through swinging arm

[BacktoBeemer]

Hi,the above bolt that holds the rod on top of the swing arm/ drive shaft tunnel (sorry for my ignorance obviously I love riding my bike but don’t know what makes it work ! )
Is very rusty and I’d like to replace it as it spoils my silver swing arm ! The rest of my bike is spotless really,it’s a 2008 Hexhead with 13000 miles under its belt .
If I undo this bolt I presume the swinging arm will drop down or worse and I’m afraid of causing more damage than it’s worth.
Any advice/ help appreciated.
Again,please excuse my ignorance

[MarkW]

If i understand you correctly the item you refer to is the paralever arm (BMW call it a "tension strut") and it controls the movement in that big joint where the swingarm meets the bevel drive.

This bit: https://www.realoem.com/bmw/enUS/showpa ... Id=33_1225

You will need to remove the rear wheel to access the 2 screws holding the black plastic cover on, then put something under the bevel drive (often referred to as the "diff" - which it isn't) to stop it dropping when you remove the arm.

This is an ideal opportunity to grease the splines where the driveshaft meets the rear bevel drive _ an oft neglected but simple bit of essential maintenance