Chosen Solution
I have a Murray 42” deck riding mower. After mowing for an hour or so the mower started smelling of burned rubber. I turned it off and left it for a few days. Upon starting again it immediately smelled of burning. Blades disengaged obviously for startup. The engine drive pulley (the one nearest the front of the mower holding the deck belt) is spinning and just shredding the drive belt to smithereens. It’s not supposed to spin when the blades aren’t engaged, right?? Why would it be stuck like this? ETA: photos of the mower, a 14hp 42”deck. The model number sticker is entirely worn off so no idea. Best guess after hours of online searching is a 2004.
s
Maggy Rhein it is entirely possible that the pulley continue to turn but the belt loosens when you disengage the blades. We would need to know what model your deck and mower are. Also, it may help if you post some good pictures of your deck, belt etc. See if you can move the blades by hand with the with the belt off (mower off of course as well). Let us know what you find. Adding images to an existing question Update (08/10/2019) Maggy Rhein would be great to have a model number so we could be specific but even generic should help out. So the pulley that drives the deck belt will always turn for as long as the engine runs. The engage/disengage of the deck is actually done by a pulley that tightens/loosens the belt enough to decrease/increase the tension around the spindles for the blades. Double check all the pulleys on your deck and double check the belt. A belt that is to short will always have to much tension and can eventually shred on the pulleys. A belt that is to loos will get caught and shred as well Here is the typical way the deck engages
This is the typical belt diagram for a 42” Murray deck
