Well it's like this: the positive battery terminal goes to the starter solenoid. So if the solenoid isn't there, you're hooking the starter wire to the battery, thinking it's the positive battery wire. That is the simplest explanation. To check this you can follow that wire and see if it goes to the starter, or you can take that wire, hook it to one of the poles on the starter solenoid, then run a cable from the battery to the other pole and hook up the small exciter wire and starter should function normally.