I've not worked on any Kaw. dfi units, but, as mentioned, it sure sounds like a gov. issue. The part about running OK with the blades on ( loaded) is one symptom.
Is the gov link spring in place? Its the small coil spring around the link rod and hooked into throt. and gov levers. It helps take up any slop in the linkage. Are you working with the Kaw. shop manual? If so, it has a pretty detailed gov section.
" But let me tell you something ,folks: You can't fix stupid! There's not a pill you can take, there's not a class you can go to. Stupid is forever!"