A worn throttle shaft and/or the holes in the carburetor base where the throttle shaft goes through it can cause the throttle plate to hang up on the housing. I've solved minor misalignment problems by loosening the throttle plate screws and tapping the plate into exact alignment with the bore with the idle screw backed off several turns. If the problem is caused by wear, it won't get noticeably better until the housing is repaired with bushings and the throttle shaft is replaced. This type of wear can also result in vacuum leaks around the shaft that can affect idle mixture and speed.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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