Sounds like its running lean, sucking air around the intake most likely. Did you replace the o-ring between the carb and the intake? How about the o-ring between the intake and the head? With it running try spraying some carb cleaner around the intake, sometimes those crack in the rubber flex part in the middle, spraying some carb cleaner or flammable brake cleaner around it you will hear the difference in the engine and know you have a leak.
Beyond that make sure the needle in the slide is in the right clip setting, and check the throttle cable is letting the slide go down all the way by looking in from the airbox side. Generally not wanting to idle down though is running lean.
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1984 Honda ATC200ES "Big Red"
1982 ATC200E "Hondie"
1988 TRX300FW "Project Quad" Still in progress....