I don't have one but I found a couple of images here where it looks like the guy made a tool to help get the belts in place? From what I have seen, you may have to remove the motor from the saw to do it. Only shows one belt but maybe this will help. You may want to replace the shims while you are at it.
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.
