circular saw low speed and smoking?

Without actually seeing what;s going on it is tricky to be accurate but it sounds as if your carbon brushes worn or jammed in their carriers. The arcing may have damaged the commutator by burning from the arc. If this is not the problem then it is most likely that you have a burnt out stator coil. Can be a home repair but it is not for the faint hearted. It involves dismantling the whole machine ,discinnecting the the wires of the coil and then repairing and insulating the repair or replacing the whole length of wire. That is assuming you can obtain new wire of corrct gauge etc. take my tip. Try the brushes and cleaning the comm with fine sandpaper (not emery cloth or board) If that doesn't do the job bite the bullet and invest in new tool. By the wayrewindig the coil neatly isVERY difficult Hope that this helps

John Mantova
March 2012