IMO someone that has 40 years experience would be the person to listen to.
Orange sparks indicate bad connection point to the commutator. Blue sparks indicate a short circuit in the armature or commutator coil. Green sparks indicate the motor is overheating and dying.
Many motor repair videos on youtube will give you an idea of whats going on but the basic gist is bad connection point of the commutator to brushes.
[MEDIA=youtube]lK191a4IV8M[/MEDIA]
Gadiel
3 years ago
all you have to do is just clean the brushes and the mating surface so that they can contact each other properly. make sure that the brushes can slide up and down freely and that the spring or whatever pushes down on the brushes are doing so properly. "