Have you changed the oil, and if so, which oil did you use?
Some oils can reduce the friction between the clutch plates resulting in symptoms similar to what you describe.
Also, having a CV carb fitted as standard, isn't going to win any prizes for throttle response.
As Justin said, if the bike is new to you, order a clutch-side gasket just in case, but take the cover off and check the state of the cam belt tensioner. This is important.
Also, as old.Indian said, steadily open the throttle rather than whacking it open works best. It's a big single cylinder with a CV carb.
Hope this helps