Belt jumping off

I hope one of you JD fellows can help me out. I have a JD GT110 with a 54" deck. As I'm doing a spring check over/tune-up I found a cracked deck belt. Replaced it with the proper JD belt, but when ever I engage the PTO (electric) the belt jumps off. Have checked everything I can think of. Pulleys look good, checked all bearings and have even tried a second belt with no luck. The only thing I can see is that the belt may be too tight. Have watched the the system while engaging and noticed that the idler has very little movement. Anyone have any suggestions, what hair I have left is going fast. Rivets

Just a thought. Is the belt routed correctly around all the pulleys. Have seen more than one case where the belt was on wrong but would still fit and work in some cases.

Yes, had the customer bring in his manual. I'm really confused. If I don't have an answer soon I will send it the the JD dealer. It will cost me more, but I want the customer to be happy. Same unit that I am having trouble adjusting the brakes. No one answered that one. Thanks for your input IL.

Did you look to see if anything was bent. All pulleys level with each other?
I had a craftsman do the same thing and it was a pulley not lined up with all the others.


Just for fun I would put the old belt back on just to see if still does it. But I am just weird like that lol

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Well after three hour this afternoon I might have found the problem. To make it short, I found that the step/shoulder washer on the tensioner bracket had both internal and external wear. This was allowing the pulleys to jump more than I like. Added a shim and wave washer to tighten it up. Cut for 30 minutes trying to replicate the problem, only happened once at the end. Jumped off when I tried to engage at it's lowest cutting height. Going to order a new washer on Monday and see what happens. Never seen anything like this before, but I guess we've all overlooked the $2.00 parts before. Never to old to learn something new, I'll let you know if it solves the problem. Thanks for the ideas. Rivets