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  1. #1
    CB750 New Member mdelaughter's Avatar
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    Aug 2018
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    Norman OK
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    Voltage drop at Key Switch

    New member working on a 78 CB750A. The bike isn't charging, at the battery I am getting 12 volts, at the regulator I am getting 10 volts with the key on and the bike not running. I checked the volts at the key switch, 12 in on the red wire and 10 out on the black to the regulator. I tried disconnecting the headlight and it made no difference in the voltage. The bike was in storage for quite a while, could there be enough corrosion in the switch to limit the flow?

    Second issue, might or might not be related, before I broke out the voltmeter I tried to adjust the regulator, turning the screw did not change the voltage out to the field coil. Bad regulator?

    Thanks

  2. #2
    CB750 Member cttrail90's Avatar
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    Jul 2018
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    Sacramento,Ca
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    I am not sure but the regulator only works when the motor is running. I would start the bike and then check voltage to battery at idle and at 2000rpm. You should get 12.1 to 12.6 volts. Voltage should come up from idle as you increase rpm.

  3. #3
    CB750 New Member mdelaughter's Avatar
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    Aug 2018
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    At idle I am just getting 10 volts. Bad ground maybe?

  4. #4
    CB750 Member cttrail90's Avatar
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    Jul 2018
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    If you are only getting 10 volts to battery when running it could be a bad ground or a number of things. At this point maybe (dirtdigger) or (amc49) can help.

  5. #5
    Moderator dirtdigger's Avatar
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    Yes the switches do go bad, if you have 12 going in but less coming out you have resistance and need to fix that first. The voltage regulators have points in them and wear out just like engine points very well could need a new regulator as well.

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