I recently bought a highly modified '63 Pan. I just bought a new battery for it and it is fully charged. When running, she will run for 30 to 45 minutes then die. Upon checking the charge on the battery, it is at 6 volts or less, and the bike will not start again. I can recharge the Battery and start the process over again- so That rules out a bad battery. Any suggestions on how to fix this? Where to start?

 

Did you set the polarity by flashing the charging system? I can't remember been to long ago... "flash"A to grd or F to grd...?