Have you been is any deep mud? I had some mud and grass get into the pressure plate one time and hold the forks from comming up all the way. That would make the clutch slip, but it is not likely to be the problem. I would make sure you get a Jap replacement (new) Asin or Dieken would be good, The lining could have also gotten hard from slipping causing it to loose it's ability to grab. Kinda like glazing your brake pads.
