Now I no why I saw a BMW with "needs a new clutch" for cheap...lol.

It appears you have a leaky rear seal by the driveshaft, or the rear drive. see if oil leaks from the rubber boot when you loosen the clamp and pull it back. These R1100+R1150 bikes are excellent bikes. I ride mine often. But they are very particular to work on. Easy to work on, but time consuming when you do it right. Be careful to grease the splines with only the proper grease. Especially with the 6 speed R1150R  bikes. Watch Chris Harris videos on the R1100RT and R1150RT.

What a mission - and no swearing 🤣 Great work

Did this job a few years ago now and the results were worth the effort. Just make sure you take your time an double check each step. You may want to look at fitting the clutch plate spacer mod which allows all of the splines full length to engage. See advrider forum.

Really helpful video, thanks for that... I've just bought one (2005, 50,000 miles on the clock) picking it up next week. Hoping the seller's truthful, was unable to take it for a test ride, failing that, at least I now have an idea of what I might be up against. Subscribed.

seeing all the corrosion and grime on this unit.. i would be forced to blow it all apart and de-grease and bead blast all that corrosion off and put her back together clean..  heck, i'd probably address the  rust on the frame and paint it too.. i just couldn't leave her in that condition..   that's just me...  i never leave well enough alone.. lol..

I'm watching!!!..............And I don't even have a BMW!....Great job. Cheers from the USA.

I have done this work twice.  Last time was on my BMW R1100RT. Few differences between those bikes. I wouldn't use a power ratchet on these bikes. Too much factory loctite and aluminum. The threads can strip very easily. You should be heating the swingarm pins before disassembly.
Watch this video before going further. You are potentially making some fatal errors.  There is far too much to tell you. This video covers everything you need to know.  You will be very glad you watched it!  Did you order a new clutch yet? The advice on getting an aftermarket clutch is sound. Also drain your gear oil and look for shavings. Transmissions are a weak point on these bikes. They are clunky (you get used to it, and better at shifting over time). Bottom line, I love ,my BMW R1100RT, and will never part with it until it is completely worn out. I have 114,000km on mine and it runs great. I know these bikes well. Any questions, I am happy to help.
https://youtu.be/6gzR4WHD-94?si=oW6owT0q6628Z4wY

That bike doesn't look like it has EVER seen soap and water.

Bit of a monster job for a clutch replacement. Good work as always Jay. It’s pretty grubby in all the nooks and crannies too, you could spend hours and hours on that!

No key for the seat or did I miss that it’s broken….?

You remove the back seat with your key. Look at 6:49 to 7:00 between the back light and your number plate. Removing the seat is a mater of seconds without removing any screws.

these clutches last forever when the bike is ridden correctly.. you can't slip the dry clutch like you can a wet one..  just dump and go..  will last forever.. well.. almost.. if the splines last.. lol.. lube them well..   this bike is daunting to work on at first..  but once you get the hang of it.. it's really not that bad..  the germans know how to engineer..

These clutches should last 150kkm easily.
You’re due for the spline lube anyways somewhere in the middle of that to keep shit together.
1150 had the clutch plate wrongly designed so it would be good to replace it with the improved part.
Apart from that these are very good bikes 1100/1150
And I consider 1100 lineup already classic along with r80, r100

Its not bad hell i have done it 3 times now including a complete motor change did the spine in the trans too new lifters 1200 Injectors an a y pipe on my 1150gs now supermoto

I had a BMW K 1200 LT in 2010. I stopped in to see a mechanic are used to work with when I was a Honda motorcycle salesman. He was now a mechanic at this BMW shop.
 he had a K 1200 LT just like mine on his lift with the trunk, bags, brackets, exhaust, seat, part of the frame, rear wheel, final drive, swingarm, driveshaft, and transmission removed. I asked him, what is up with this when I stopped back in his service department area. He said the slave cylinder leaked because the guy never changed his clutch fluid, and it leaked on the clutch. so it needs a clutch
  no, this was in 2010. I asked him what is this gonna cost the owner
he said around $4500 including parts .. plus Shop materials, plus disposal fee, plus tax
that was 14 years ago. I am guessing that that job now as well over $6000-$7000

If it's not too late, how about removing the lock barrel itself? Have a look on YouTube on how to do this.

Great video! I’ve been thinking of getting one of these as a project. They are not very expensive and you have taken a lot of the mystery out of getting stuck in.
    One thing - do I also need to buy Crocs for all this to work or can I get away with different shoes 😊

Iam watching and ride a st1300 😂

Its not "hard" I wouldnt say , its just removing bolts and putting them back init ,so , its just a pain in the ass to be honest . I`m on my 5th 1150RT and I have had to do the clutch on 3 of them , lol . Glutten for punishment ..lol