Originally posted by jfc_tech
Maybe i just use my feel & touch things. The clutch nut measurement is actually a matter of engage early or later...so i think i manage without "digital measurement". I just use my "analog" caliper
Julius and Michael mentioned before that the setting in the manual is just for reference only. Like what you say, it is not scientific. Most of the time, it is by feel and touch like what you say. Of course, it depends from engine to engine as carb settings and pipe config can affect these settings.
Anyway, what they do is to set it tight. Go on the track and test the clutch out. Begin to loosen the clutch (you can do this externally) 1/4 or a turn each time till you get the best punch with least clutch slippage.