Hy Barsteel, as you said one side of the ammeter is connected to the battery positive terminal, the other terminal has one wire which is spliced in the harness to the ignition switch, the headlight switch, and the Bat terminal of the voltage regulator. You said you have replaced the starter, are you aware that the six volt and twelve volt starters have different pitches of starter drive gears, so you need to use the flywheel which goes with the starter. You can safely use a six volt starter on a twelve volt system, as long as your engine starts quickly, so you must maintain the engine in a good state of tune, to prevent overheating the starter, hope that helps.
