With some knives that have screwed-in stop pins, I get good results by completely loosening the pivot pin, then screwing in one side of the stop pin to a normal tightness, then screwing the other side in just until I start feeling resistance from the handle scales (as opposed to resistance from gunk in the threads). Use Loc-tite to hold the screw in place, and then tighten the pivot as necessary. In screw-in setups the stop pin itself is generally a touch too small to act as a proper spacer, so you have no choice but to do a balancing act.