Mikuni Carburetor Jet Needle Type 5FP17 The Jet Needle controls the fuel mixture in the mid-range 1/4-3/4 throttle position The taper of the needle determines the amount of the fuel For example: the thinner the diameter of the needle, the more fuel will be drawn The thicker the diameter of the needle, the less fuel can be drawn For TM32-1 and TM34-2