[G.M.]

The best bet is to carry a 12 volt battery jumper pack. The one I use
has a shut off switch. This allows you to put the cable clamps on with
red POS to red ground on the 6 volt battery and the Black NEG to the
heavy cable at or going to the starter. With someone inside to turn
the ignition switch on and work the gas have them turn the switch on
but do NOT push the starter button. Now when ready you can turn the
switch on the battery pack PUTTING 12 VOLTS TO THE STARTER ONLY.
This way 12 volts is not introduced into the 6 volt system. You can even
do this yourself by working the carb by hand. G.M.