Ive heard more than a few times that most carb problems are electrical.
I have a little honda nighthawk project ive been working on and the darn thing wouldnt run off idle worth a darn because the battery was shot. After 4k ( it goes to 10k ) she was good because the alternator could keep up with the increasing demand on the ignition system. If your charging system is suspect, you might not be getting enough juice to make a good spark at bigher rpms. Like Monte said, you dont get full compression with partial throttle. As you open the throttle the compression increases, and increased compression requires a stronger spark.
Anywho, one thjng you could do to help determine if fuel starvation is the issue is get the bike going as fast as she will allow, simultaneously pull the clutch and cut the engine, and read the plugs right on the side of the road.
