Like was said , there's no adjustment screw . The shift drum isn't adjustable either . Make sure the 4 hold down bolts are tight too . There might be a bent shift fork but that would be evident looking at them with the cover off .
Your service manual shows the relationship between the gears and shift forks and where they should locate in each gear .
Disclaimer : Don't believe anything I say unless you are absolutely sure that I know what I'm talking about .