All my pulleys are alligned, ive replaced the belt and the idler pulley, still get that belt squeal scraping noise. what else could there be?? everything is tight, the belt has proper adjustment, out of ideas..

 

Check to make sure nothin is seizing up.

 

Make sure the pulleys are clean and free of any oil or any other material. I even go so far as to take a scotchbright pad to break any glaze that may have formed on the contact surface from previous belt slippage.

 

probably have something dragging. Take the belt off, turn everything by hand, if something feels harder to turn than you like, replace it.