I have a Jet contractor saw that recently started vibrating. I can see
the belt bouncing when the saw is running. I had never replaced the
belt after about 4 years of moderate use. I thought the belt was bad
because it was worn enough that it was sitting low in the pulleys and
everything appeared lined up well. Replaced the belt with the correct
sized green belt, for mowers and the like, but no improvement.

It was then I notice that the motor mount bracket *may* be bent. It is
a stamped steel bracket that hangs on the bottom of a cast iron mount.
Just past the mounting pin the steel bracket has a slight bend to it,
about 5 degrees. I don't recall if this bracket is supposed to be bent
or the weight of the motor has bent it.

Is the steel bracket that the motor bolts to supposed to be bent
slightly or should it be straight?
The bracket that I am talking about is #113 on page 18 of this manual:
http://www.wmhtoolgroup.com/partfiles/m_708301.pdf

If it should be straight I can probably straighten it and reinforce it
with some angle iron.

Are the link style belts that much better than a standard belt? (the
belt I just bought was $12)