Much of the text in BMW parts fiches reads like it was translated from German and can be slightly confusing in English. What I believe it means is that if your moto's clutch rod has the bushing (a separate piece #14) indicated by the red arrow in the attached drawing, and if you're buying the new-style clutch piston assembly, you'll need to remove that bushing for the rod to work with the piston; if you're unable to remove it, you'll need to replace the rod with the new-style rod. The attached drawing is of a K100 rod. The K75 clutch rod has a flare near the end where the rod diameter is reduced. I drew a red triangle on the drawing to indicate it but there's a photo of it in the
Max BMW fiche.
If your diagnosis is based only on an
understanding rather than actual visual confirmation, you might want to verify the source of the problem before buying parts. You could always post on YouTube a video containing clear audio of this noise, then post the link here. Bricks can make impressive doomsday noises for differing reasons.
Does the noise change when the clutch lever is pulled? Is it a rattle, a grinding sound or a rumble?