Thu Jan 17, 2013 12:26 am by 56-S-Fan
If the 12volt battery was only used as a jumper to try and start it, its not very likely that you did ANY damage.
If you left it connected after the motor started and was running, you then become at risk to damage the generator and voltage regulator, ignition coil and 'perhaps' some of the gauges.
The problem is it all depends! For instance, you cannot burn out a bulb if it is not on. You cannot burn out a gauge if it has crappy, i.e. old connections that have high resistance, and the voltage at the gauge is say, only 8V instead of the expected 12V.
When you are jump starting a 6V system with a 12V battery, ask yourself what is being 'exposed' to the 12V. Well, obviously the starter, and starter solenoid, ignition coil, and key switch. All of these are pretty robust and can take a 12V jump start many, many times before failure. The item that is most at risk is the 6V coil. That being said my S132 was converted to 12V at some point in its life and the 6V coil was never replaced. I changed it when I gave it a tune up and discovered it was 6V. So its also hard to predict what will fail at the higher voltage.
By the way I have done the same scenario many times on my S-120. Then I fixed the weak 6 V battery issue by installing a proper ground from the battery to the frame. Starts and runs like a modern day car, well, almost. I don't know the details of your situation, but it has been stated ad nauseum, that proper battery cables (like 0 gauge) and a propery ground are essential for a 6V battery system to perform properly.
56 S-120 4x4 started the whole mess.
S-132 dually longbed,
S-120 4x4 Travelall,
S144 Forestry truck,
S160 Holmes tow