Making sure the idle is set to spec. is normally the culprit.
If it still does it. double check the motor mounts, to be tight and secure. It looks like you've had the motor apart recently and if you've moved the engine forward enough, that would be the cause.
Remove the belt cover and as the engine is idling, the only pulley that should spinning should be the front one, could try cleaning the front clutch with brake cleaner and compressed air as they do get dirty thru the years of use and sometimes get crudded up enough that they don't release completely.
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