Electric Motor: Spark and Repair Issues
Because continuity, alone, is an indicator of nothing.  

Actually, you've got way too much continuity!  But you are not testing for that.   You should test the resistance of the coil, better, measure its inductance.  Not happy stuff.

This is the crux of your problem.  You have a shorted coil.  It's very obvious, from the big arc flash coming from the receptacle, that the coil is much lower impedance than it should be.   That kind of arc flash is TROUBLE and you should not provoke it. 

The arc flash occurring at  the coil itself is telling you what's gone wrong.  Some of the varnish insulation has failed and coils are shorting.  You need to rewind this motor.