How easy should starter motor turn by hand?

I'm not getting the engine to turn over when the starter button is depressed. I can hear the starter motor but the engine doesn't engage. I thought at first it was the Bendix but after taking it out it looks perfect. Next I took the starter out and it is pretty difficult to turn by hand. I'm wondering if it's got bad bearings and won't spin fast enough to throw out the Bendix and engage the flywheel? So how easy should it be to spin by hand? Thanks