Motorcycle Repair: charging system on a 1980 cb750f, bike check, cb750f

Question
i put a ne bat. on and the bike will run till the bat. dies. what could it be

Answer
The first thing to check is that the charging system is working. If you have access to any kind of DC voltage tester attach the tester positive to positive and negative to negative on the battery posts with it installed in the bike and start the bike. Check that the meter reads at least 13.25 volts when running. If you don't have a meter take it to a parts store that offers charging systems tests for free and have them test it. If the bike is not charging it could a few possible things. The field coils in the stator could have gone bad or the voltage regulator has gone out. Have the charging system checked first.