Yeah, probably a plugged passage. If you haven't yet taken the carbs apart since you got the bike, it's a good idea to give them a good cleaning. I'll be cleaning them for the third time this season to get those last gremlins out.
Make sure you get all the rubber seals out before you start blasting them with carb cleaner, or boiling them. That includes the butterfly seals, and the tiny little rubber o-rings and washers under the idle mixture screws.