Hi Kawabob1,
Your AYP made mower aka Craftsman 917,xxx,xxxx has, if I remember correctly, 1/2" x 93 1/2" deck belt. You've stated in your #1 OP post that you're using something non-OME that is 5/8" by XXX" in size. Check that and make sure that it is, without any doubt a 5/8" in size...