I think Bertsmobile is correct. Rust. Factory puts these mowers together DRY. That is why these parts rust in place, whether you store unit indoors or outdoors makes no difference. If PTO belts off, and engine still locked up, may be PTO shaft pillow block bearing assembly frozen. I have front mount deck on my Hopper, so that may not apply in your case. To get clucth off of engine stub shaft, use pneumatic innpact hammer, chisel bit, seat in pulley groove, tilt impact hammer gun opposite direction you want pulley and unit to go and see if the vibration won't just walk the thing off. Worth a try, being as you can get a pneumatic impact hammer at Harbor Freight for under $20, and they usually come with a chisel bit. Look on You Tube for video. On my mower, no way to attach gear puller, and with the stamped steel pulley, would do no good anyway. Not familiar with your unit and it's layout. Acetylene rig is another option, just cut it off in pieces, and try to not damage stub shaft. (I dread the day mine goes bad because it is original unit I thimk, and is sure to be rusted in place) Hope this helps tho.