hey cr125freak, I've got the same bike. Just a few quick questions of what you're running because I also live in Ohio and with weather and humidity pretty much the same figured I'd just ask. What premix you running? And as far as jet sizes and clip position on the needle where you at? I basically had same symptoms you had. 1/2 to full throttle, fall flat on its face. Found I was too rich, fouling plugs.... so made adjustments and is running a hell of a lot better, but I know I can squeeze a little more out of her. Just had a rebuild over the winter and has not been at its total potential yet.
Thanks,
Chad