...one last thing to try before you get your OEM belt.... Make sure that any and all tensioning springs are hooked where they are supposed to be hooked at both ends. Sometimes we "forget".:laugh: Where is the belt jumping off, can you tell? Check the vertical AND side play in the pto/deck drive bearing/pulley. I'll bet that is where it flies off when the clutch kicks in, the variance in the belt profile is probably what's causing it though.