Pulling a cable is a very risky way of checking the generator output. It's a lot simpler to ground the Field terminal at the generator and see if the voltage rises when the engine speed is increased slightly (the lights get brighter). Don't overdo it- - - -I've seen a 12 volt system go above 20 volts with the field grounded with only a moderate increase in engine speed. Pulling a battery cable can result in a voltage spike of around 100 volts in some cases. I've seen it on an oscilloscope several times.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!