The last time I used a Sawzall on a 300w generator, I found that it cut very quickly through the plastic housing, but as soon as the blade cut through into the generator itself, I encountered a lot of sparks, and the hair on my arms caught on fire.
Later, the doctor said I had suffered an intense electrocution, which led to a massive cardiac arrest.
Please do not use the Sawzall (at any speed, and especially not at full bore) to kill a generator. The generator will win, every time.
HTH,
Rick
(sorry, J/K . . . I must have mis-read the meaning of the post) :: :: :: :: :: ::
Rick