Motorcycle Repair: battery not staying charged, 1979 honda cb750k, cb 750

Question
1979 honda cb750k, will worn generator brushes keep the battery from staying charged? battery seems to get stronger if it sits, does this mean the battery is ok? If voltmeter is connected to battery while running what should the reading be?

Answer
Hi Richard, uh I dont think the cb 750 had generator brushes. I think it used a Stator with a non permantly magnitized rotor and a field coil winding to generate the magnetic field. I could be wrong.  honda did switch to an alternator but Im sure that was years later??? Static testing of your battery with a voltmeter only gives you a surface charge reading. It is usless in determining the condition of the battery. There are two ways to test the battery for it's condition 1: Specific Gravity per cell. This is done with a Hydrometer. 2: Carbon pile load test. This requires a machine available at Shucks or a service station. The first test I mentioned is the best for a do it yourselfer and is very accurate. The Voltage at the battery with engine running at approx 2000rpms should be 13.8v to 14.5v and should fluctuate with rpms. If your voltage is below the batteries surface voltage then the bike is discharging and some more testing is required.

 regards
     randy