Inside the clutch case there is a little lever thing that pushes in the clutch. Check this. If on the end of the lever you can see silvery metal, you need to replace it. Also check to see if on the main clutch pad the bearing. It should not be worn, and the bearing should spin freely. But as Brett said, drain the clutch and refill with 20W-ND so 30w-ND. Very important.