Hi Tom, I have a 2001 315R with the same problem. I purchased a set of clutch plates from BVM Moto and the ELF oil
These are CR250 plates. I've just fitted these and the difference is amazing no drag whatsoever.
However the new plates are slighty thicker and they foul on the casting when operating the clutch.
I got round this by adjusting the free play on the master cylinder to reduce the stroke of the piston.
Do this with the engine running.
Its a simple job...drain oil, remove 4 bolts on the cover, 6 bolts and springs, remove plates, I oiled the new plates
before fitting.
I've fitted my a few days ago and its made a big difference, but time will tell....
Hope this helps
Steve