As you look down the venturi from the front of the engine, you will see a needle protruding from the left side, and a spray bar from the right side. You want this 1/8" gap between the two when at full throttle. If not, adjust the low end. The low end adjustment is the small slotted screw on the left side of the carb (looking from the front). This screw will adjust the needle that you were looking at in the venturi. Turn the screw CW to close the gap (leaner), or turn it CCW to increase the gap (richer).

While I do not own a TH 46, a 1/8" gap seems a bit excessive to me. Another method to initially make this adjustment is to attach fuel line to the carb's input nipple and blow into the fuel line. Make the low end adjustment so that you just start to hear the air coming out of the spray bar.

Good Luck and holler if you need help.