You said you had this problem when you nailed the pedal to the floor? Maybe you shouldn't nail the pedal to the floor. This is a big problem on 4 stroke motorcycles and is only magnified by the single cylinder, small intake, and lack of accelerator pump. It's usually refered to as the 4 stroke hiccup. The only way to prevent the hesitation is to roll on the throttle instead of rip it wide open from idle. The hesitation is caused by a momentary loss of vacuum in the intake because you allow more air to enter the intake, but the cylinder is still drawing the same volume. The speed of air moving across the jets slows considerably, and fuel can't be drawn into the incoming air as efficiently. Most car carburetors and some newer dirtbike carbs have accelerator pumps which inject fuel into the incoming air during this low vacuum period. Dirtbikes also have a pilot circuit to help the carburetor move from the idle to the main cicuit and you have to tune and tune and tune to get it perfect. Even slight changes in weather can throw it off. In conclusion, it sounds like you're hitting a lean spot coming off idle. Or, your TBI setup is too large for the engine and the engine cannot maintain vacuum while the butterflies open.