have you checked the operation of your choke? choke cable sticking? mine will do the same thing when it warms up. when i get that stutter at about 5000 rpm i know the motor is warm and its time to push the choke in.as for rotors and charging, try cleaning the wire plug harness under the left side cover.this corrodes after time and will impede the electrical system. actually, on a bike this age, best to go through all wire connections and clean, then use dielectric grease. hope that helps ya´ll. 81´ 650c 40k a-o.k.