First thing to do is check the battery
If the rectifier went dead short then it will drain the battery as well as burning up the stator
So it is jumpers from the battery poles directly to the engine ( ground ) and the + on the starter motor
Motor spins= battery good ( as the starter has already been tested & confirmed to be good ) .
next repeat without the ground jumper
Starter does not spin = bad ground connection
On the top of the battery wire on the starting solenoid should be a thin red wire that goes up to the B terminal on the key switch
There will be a fuse on this wire somewhere .
I have no intention of typing out the entire electrical section of the service manual because you can get one yourself by going to Cub , and entering your model & serial numbers
If you have troubles following the instructions then come back with your specific question.
Plenty here who will happily walk you through but we are mower technicians
, not typists.