If its new then the engine is still not broken in. They're extremely tight when new and can sometimes react a little funny (bogging, backfiring, etc.) It also has to be warmed up real well before it will run right.
A bog can come from more than just the carbs. It can also come from too tight of an engine, and/or incorrectly set clutching. Since you're in NY, I have to assume that you're trying to drive it on the dirt (not recommended). That clutching is not set for dirt, it probably would engage too low. Add that to the tight new engine, and you have yourself a bog.