Welcome as the newest resident here in "the home."
If you ask a question for which we don't know the answer, don't fret, we will give you an answer with great confidence anyway.
The photos show that I have a buck in my pocket from some previous owner of the bike. I refer to the backrest.
I have seen them go a few thousand miles easily on a transmission showing flakes. If you have a known good one as a spare, that is the time to install it. Even the first time you can do it in an afternoon.
You must answer a basic question, why do you have it? Is it to ride, or mostly as a project to fondle and cherish and sometimes ride?
Consider getting rid of those crashbars. They are dangerous. Google the subject.
Almost anything that you could want to know is already documented well on the Internet. Google is your best friend. Some people that have a keyboard feel that they are experts, but aren't. Of course we don't have such ilk here on boxerworks.

Often you can get the info needed faster off of the Internet than here. We strive to offer up contradictory advise and degrade the thread to total chaos.
Then there is Diane.
Did you start a logbook on the bike? Record everything you touch, find, fix or think needs attention. Write down what you got for history from the PO. You may want to keep it in an excel file, or on the computer.
You are on the right track by checking things often, such as this transmission.
Did you check the charge voltage? Have you checked the flow rate from the petcocks? How about lubing the wheel bearings and swing arms? Do you have fork stiction? You can keep busy with diagnostics that could well find something amiss now.
If something seems that it needs to be forced, stop and ask here first. We are saddened by folks that come by and have owned other bikes and applied that wrenching to the BMW. We see folks have to spend ten times more due to not asking first. Don't make well known mistakes. Don't reinvent the wheel.
Ask the Indians what happens when you don't control immigration.