Hi Greenhorn, thanks for your help. Are you saying that there is a floating spacer on the shaft, and the extra shim needs to go on the end of the spacer, below the inner ring of the top bearing, so it will limit how far the inner ring of the top bearing can be pushed down the shaft? It has to end up with the pulley nut clamping both inner rings, so that sounds like what you are saying. Then the outer rings would float just a tiny amount in the housing.
That would mean the previous tenant had dismantled the whole assembly then removed a shim from the spacer below the top bearing, and then put it all back together? What a lot of work he did just to make the mower unusable.
How is the bearing to be removed? I'd have guessed it was easiest to take off the nut and pulley, then push the shaft downward right out of the housing, so you could knock out one of the bearings by tapping the housing against a bench or anvil?
