Sluggish Motor?

If you find a sewing machine motor that seems tired - lacks pep and vitality - is slow to turn; the armature may be gummed up with carbon. The solution is to either replace the brushes, clean off the armature, or execute a motor burn. Cleaning the armature is a risky process in which you must avoid damaging the armature surface and the wire coil while removing the built up carbon. Using a brush, wire brush, emory cloth, sandpaper, or even a Dremel tool it is possible to clean the armature, but be very careful. (Always unplug form power before trying to work on a motor.)