i like to go over the electrical system before i do jetting because if you dont have a strong enough spark you will have a hell of a time getting it to jet right.
check the pickup gap and that the flywheel is free of rust, then check to be sure you have good ground at coil and engine to frame.
then make sure you have a oem stator and cdi. lots of junk aftermarket stuff out there that will cause this exact problem
be sure you have a clean air filter!
once everything else is good then you can start jetting. what pilots have you got in and have you tried adjusting the air screws at all?