Also you could be too rich on the primary side for jetting. as it was suggested check the APT.
Check your pump stroke it may need to be larger stroke or decreased.
Check your choke if so equiped, it may not be opening up fully.
Your Power Piston may need a weaker or stronger spring.
A vacuum leak could be at the Throttle shafts.
Which Carb do you have, a number of the unit