Glazed clutch plates do not retain oil and can cause a hard "cold stick". I de-glazed with coarse scotch brite & then thoroughly cleaned which seemed to help. Also check for correct amount of clean gearbox oil. Check your hydraulic clutch rod throwout is within spec and that the seals are in good condition with fresh fluid and properly bled and that the lever is adjusted so that it has sufficient travel. Beta offer two thicknesses of friction plates, 3.0mm and 2.7mm. Check that your bike has the correct combination of plates fitted according to the parts diagram. Some bikes have six 2.7mm, other bikes have two 3.0mm at 1 & 6 with four 2.7mm in between.