A few days ago while chopping leaves with my riding mower, I heard a bit of a whine above the sound of the motor and blades. The bearings on the belt-tension pulley had failed, and the whole assembly was turning on the bolt.
I replaced it, then found noise and severe drag on the PTO pulley. I was afraid it was dirty, dry bearings. I wondered why the drag didn't keep the belt turning with the clutch disengaged. It seemed noisier than the bad pulley. I wondered why I couldn't hear it over the motor.
Aha! When I turn the crankshaft with a wrench, the pulley doesn't move. It's not bad bearings or a dragging clutch. It's a blade brake! Dang, now I've got to get all muddy putting the deck back on.
Why didn't you ladies and gentlemen tell me electric mower clutches had blade brakes? I'm going to have to file a report on this. What's the complaint address for alt.home.repair?