Hanging idle

Perhaps the throttle cable is adjusted too tight or is hanging for whatever reason such as internal fray, lack of lube, twist grip issue (such as for example the rubber grip rubbing against end of handle bar; throttle grip sleeve not rotating freely around the handlebar).

With engine off, and throttle grip slightly opened and then slowly returned to closed position by hand, there should be a noticeable click as the throttle slides fully close.

Could disconnect the throttle cable at the carb, and operate the carb manually (open and close) to see whether the issue persists. Which may indicate or rule out the possibility of a cable issue.

Good Fortune!