Thanks for the reply, cletis.
Are there any ways to ID a 6v starter from a 12v? It had a sticker on it, but I can't read it. I thought it would be a 6v because it was a kick starter, not a solenoid starter. The starter contacts (pushbutton on the starter) are a little pitted, but I couldn't get in there to smooth them.
The ground strap on the battery is the heavy braided factory type, but it could be corroded. I'll clean the contacts on that. Next weekend, I may try to start it with a 12v battery and see what happens.