Grab hold of the flywheel (not running, Duh) and see if you can move it fore and aft. It should not, except for barely detectable if you are sharp enough.
I’d say more common, at least for roller bearings, is you can hear them before they get really loose. I think of it as the sound of a steel wheel on a rail, if you are old enough to remember streetcars. Or the old steel wheeled roller skates on the sidewalk. Revealing my age again.
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