A couple of things for you to try. It may work it may not. Most of the time it works for me.
Do you have a full tank of gas? If so try half a tank and go for a spirited ride and try to do a few WOT runs and it will clear out. Make sure you dont have a split air box other wise debris gets in the carbs. Your filter screen in the gas tank maybe deformed enough to the point of not being able to filter.
We are so glad you have overflow tubes.
One trick you can try is to drain the bowls and blow compressed air (not too high a pressure- low pressure) into the vent tubes and that might blow any debris past the seat and needle. This trick can save you from pulling the carbs. Refill and drain the bowls checking for debris and repeat if not clean. I wonder if the tank vent line is pinched.