they are power rated belts. the pulleys seem to spin freely and smooth. They did not look deformed when I was spinning them. It would also just fling the belt off also before it broke. How tight are they supposed to be?
On a more helpful note, now that I have read beyond your second post, I'm going to say you MUST have some sort of pulley alignment problem. I rescued an older Massey with belt alignment problems and it would wear in one particular spot on the belt for some reason, I'm thinking that may be what you are experiencing. Can you get at those two mule drive, or guide pulleys and figure out why they have some "toe-in" as you called it? Might be bad bearings, might be a bent shaft. You can probably get replacement pulleys somewhere local.
Welcome to GTTAlk, by the way. We would love to see pics of your new tractor.
I have a14 and 16 The 16 has the pulleys straight and had a belt throwing problem so I made an L shaped bracket for the drivers side pulley to keep the belt on. No problems since. The 14 had the toe in on the pulleys and never had a problem with the belts. I'm guessing the problem is the deck spindles with with bad bearings seizing. The spindles CAN be welded up and machined back to specs if that is the case. I'm guessing the toe or no toe was a change in design later on.
I was told by many that you can't do that but I remembered that I had a V8 crank welded and recut 50 years ago. All they have to do is weld the crank up, Flame heat and cool slowly to take out the temper, machine it, and reheat and retemper. l have a WW 2 machinist book that shows how to retemper by heating steel to different colors and cooling in oil.
From what I was told from the previous owner, the deck bearings were replaced. I got the pulleys straightened out today at work and got a new belt. About 30mins of cutting the grass when I got home the belt broke. No other nicks in it this time. Also the belt was hot when I picked it up. Almost too hot to touch.