bad throttle response at low rpms

I tried taking it back and the owner himself told me "WHat did you do to it? it was running when you took it home, Wasn't it?"
I wanted to punch him in the mouth!

Oh! as it turns out... I have accepted a new job in the N.W. so I may have to part with my old buddy "Frank". Im hoping one of you wise mechanical types can find a place in your heart and home for this guy in need of a lil tlc. He runs strong when he is breathing right. $1500 obo in good condition with newer tires and more carb parts than you could shake a stick at!(including rebuild kits) I will be posting in the for sale category also.