I'm getting a little frustrated with your stubborn refusal to do a little simple testing. Try removing the switch from the top of the starter (one cable connection and two screws) and check it for continuity while it's removed from the starter housing. I have a feeling that the small stud is shorted to the switch housing, (It's supposed to be insulated.) and the conductor that normally makes contact with the main terminal during cranking has probably been burned away due to the short. It's pretty obvious that you do not understand the function of that small terminal which was not even included on starter switches for 6 volt systems. You've either got the wrong switch or the wrong starter. We need to find out which is the case before doing anything else. If you're trying to crank a 12 volt starter with 6 volts, you're on an impossible mission- - - - -it will NEVER crank the engine at the correct speed.

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!