I set the air screw, seat of pants on the rest. Check the plug after each ride. A plug chop is just for reading the burn ring in the top of the porcelain, thats it. You can feel the main when its right, and the same with the rest, it pulls the hardest. Lean pulls weak, and rich just flounders. Generally, the plug will tell you also, wet or dry? You will never jet a bike with a mechanical issue somewhere, denial does not work either. Overdue for a rebuild, a half arsed rebuild, polishing and other garage brewed mods, timing and the list goes on, and you will never be able to jet it. If you make changes more than 3 sizes, or it seems to make no difference/puzzling, its not the jetting. Start with everything within spec, keep accurate notes and time on the engine hours.