I have a 2003 Murray Lawn Tractor, model #425007x92c. Whenever I engage the blades, the belt gets looser, and when they're disengaged it is tighter. It's a new belt and I know that it's the right one. I followed the diagram to put it on. What else could be causing the belt to not fit right?

Thanks for your help.

Tony

Either you installed wrong or it's the wrong belt. There just isn't much else to explain this issue. The most common error is getting the belt on the wrong side of the tensiopner pulley. Here is the manual and I think the belt stuff is around page 342. http://bsintek.basco.com/MDEXResultsPages/PDFDisplayPage.aspx?fileName=UekmAEQLnfBhU7y