Could be a couple of things here, if the main jet is clear it could be that the air filter or air feed is restricted making it suck that hard it collapses any air ducting, thus drowning the engine! It could also be a bockage on the exhaust. The final check I would make is to be sure the breathers on the carb are not blocked. It certainly sounds like the motor cant either breath in of breath out, the creeping speed up is because it isnt looking for a sudden rush in either area. The previous answer of the blocked jet is most probable though. Not familiar with the bike, my work is 'off road' but all engines are basically the same in function
Rob, South Wales, October 2009
