Just looked at the ball joint of my 1150GS, the rubber cover seems to be split, are these available ? don't want the expense of changing the ball joint as it does not seem to be worn, just for the cover. many thanks, Dave.
Only 33p from a main dealer, save yourself 5p.
Just had mine nicked for the second time.
Are you talking the plastics Black Cap or the rubber boot?

From the sound of it, I'd say it was the rubber gaiter over the ball...
Like Dave says heat to release the nut and big torque + loctite when it goes back on.