The part of the carb that is effective just off the idle when you open the throttle is the pilot jet.
This gets blocked very easily especially if the bike has been standing for some time and especially with the crap gas that we have to put up with.
Unscrew the pilot jet and clean through the pilot jet with a thin wire.
You need a 0.016" diameter wire---a number 78 drill bit is ideal.
look down the pilot jet and you will see a small diameter hole deep across the carb body.
If using a drill bit then use some adhesive to bond the drill bit into a length of plastic tube (the extension tube from a can of WD-40 is ideal).
Suggest using new fresh gas as well.
HTH and let us know how you get on.