So my GS is finally home – been a long time coming with a rebuilt gearbox, new clutch plate and third input drive shaft. Its a real shame that this design fault still remains, its a non service item but really would benefit from routine lubrication but with complete gearbox removal and bike strip down required its a difficult and long job to do. At the same time a new clutch hydraulic slave cylinder has been installed, which I know was leaking. The story is that when BMW introduced the hydraulic clutch design they miscalculated and inadvertently moved the clutch disc 8mm further forward towards the engine and off the transmission splines, this results in the splines of the clutch disc falling short of the input drive shaft hence the wear. Apparently Brunos Machine and Repair have a fix so I am on the case now for the new shaft design.