Check that the arbor shaft spins freely. Maybe the bearing are freezing up??

Take the belt off and see if you can turn the blade by hand.

 

I would agree with checking all the moving parts to ensure nothing has frozen. If you determine it is the motor, sometimes just blowing the dust out helps. If it's a capacitor they are fairly cheap and easy to replace. There may be a centrifugal switch that's acting up. If you don't want to troubleshoot the motor, you could take it to a motor shop for diagnosis…the one I use doesn't charge for the diagnosis if you have him do the repair.

 

I took the belt off and the blade spins fine.

 

I plan on taking the motor apart later, but I am not sure I will know what I am looking at. I remember replacing some brushes on a motor in shop class, but that was about 20 years ago.

 

Mr. Childress makes a good point and that is certainly an easy one for you to check yourself. While you have the belt off, check to be sure the bearings on the motor spin freely as well. As far as the electrical is concerned, I used to service automotive shop equipment and the most common cause, when I saw a problem like you are describing, the problem was usually a start capacitor on the motor. Most industrial grade electric motors use a start capacitor to add a little extra juice to get the motor up and running on start up. First thing to check is to see if there is a start capacitor on your motor. Most motors will have a little sheet metal bump (not the one where the wires are tied into the motor) that houses the capacitor. If that capacitor is bad (and after 20 years, I would not be surprised at all), the motor will usually never get up to full speed and power. These usually are not difficult to replace. The hardest part is finding the appropriate replacement capacitor. If you aren't comfortable with it, any electric motor service shop should be able to do it without spending too much. They, of course could also tell you for sure if that is the problem.

Doc

 

Sometimes running the motor with no load for 1/2 and hour can
smooth it out - with motors that need oil especially, but on sealed
bearing motors it can't hurt either.

Don't spray WD40 into the bearings. If you did, the grease may be
dissolved in the bearings.

 

Since you're going to sell the saw on CL anyway, why not try a few things yourself, then advertise in in its present condition? Granted you won't get what you would for a running saw but it won't be your headache to fix. Spend the time enjoying your new saw. Good luck.