Your right about the venturi but if you look down the carb at the throttle butterfly you will notice it never fully opens and there is a large screw holding it in place. All you need to do is cut the throttle stop so it opens all the way and cut the excess tread off the screw. Some carbs have a swirl in the intake manifold that can be removed. Note I cannot guarantee a perfect running motor through all rev ranges but works well in a kart as most the time your full throttle.
