I'm still concerned with where the battery ground cable is attached to the frame. If you've got a dirty or corroded connection there it will interrupt the circuit for the current to return to the battery and prevent the starter from flowing enough current to turn.

Let's do some Ohm's Law math. A 6 volt starter needs to flow around 200 amps to crank the engine properly. According to Ohm's Law, amperage equals voltage divided by resistance. If a headlight in a 6 volt circuit is flowing 10 amps, for instance, the total resistance of the circuit, power, to headlight switch, to the dimmer switch, to bulb, to body, to frame, and back to the battery is going to equal 6/10 of one ohm. That means the current negotiates at least 6 or 7 connections. Even one dirty or loose connection results in dim, or non-working headlights.

Now let's try the same math with 200 amps of current- - - - -6 volts divided by 200 = 0.03 Ohms!- - - -yes, that's 3/100 Ohms of TOTAL circuit resistance! One dirty connection totally disables the starter! Actually, since battery terminal voltage under starting load is usually less than 5 volts, the total circuit resistance is more like 0.025 ohms or less. That's darn near dead short conditions!
Jerry

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