Sorry Florence, nothing personal, the ones i meant were the ones who go to a parts bin and fit something from another bike.
The design of the clutch operating mechanism does tend to let the clutch slip on takeoff and power changes, my first one did for many thousands of miles and when i took it apart measuring everything all was still in book spec, i have a parts book with hand written notes( from the us ) that says use a different number plate and spring, i think from 450 twin