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Thread: charging system

  1. #1
    CB750 Member chuter's Avatar
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    charging system

    Need to run this past someone to make sure I am doing this right. 77 750f, voltage at battery when running is only 12 vdc. I disconnected the connector at the stator and rotor assy. and checked the resistance of the rotor.resistance was according to manual. checked stator resistance and also ok with no shorts to ground. When I power up the rotor with 12 volts it seems to magnetize ok. Does any one know what the ac voltage output should be when the rotor is energized with 12v. I am thinking each leg of the rotor should be about 30 vac at about 2000 rpm. I'm only getting 10 vac and it does not seem to change with rpm. Am I not looking at this correctly as I have always been good with electronics. It is a simple system at least I thought so. Input would be helpful. Chuter

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  3. #3
    CB750 Member chuter's Avatar
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    amc49 Thank you. I will spend some time in the garage today. What you posted will keep me from second guessing myself. Thanks again. Chuter

  4. #4
    CB750 Member chuter's Avatar
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    amc49 I read your post and went through everything very meticulously. All wiring and connectors were checked and cleaned and reconnected. all check ok.
    traced connections and wiring for the rest of the bike. All checked ok. I could find nothing wrong so I ran the bike and jumped from the battery+ to the white wire in the connector to the rotor. It took a few seconds but low and behold the VOM read about 13 vdc at the battery. Raised rpm to 3000 an VOM read 14.5 volts. Voltage regulator is not working correctly. I have one O/O. It took a considerable amount of time but with a little help I finally have it figured out. Now I will install the new V/R and test and reassemble. Hopefully then I can put it away for the winter. I do not know if I will have to make any adjustments to the V/R once it is installed but I'll see. Thank You; Chuter

  5. #5
    CB750 Guru amc49's Avatar
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    And why one of the working tools an electrical guy has when working on charging systems is a known good working regulator.

    Good luck with the rest of it............

  6. #6
    Moderator dirtdigger's Avatar
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    If you are using an used original honda regulator you more then likely wont have to adjust anything. I have never had to adjust an original regulator on these.

  7. #7
    CB750 Guru amc49's Avatar
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    X2 on that one, you should not have to adjust anything. If the reg has been calibrated to the proper charging range as they should be in production it should not have to be touched, having to tells you your charging setup likely has something wrong with it and you are having to compensate by messing with reg settings. I have never had to reset a reg on any type I ever worked on and that's a LOT of charging systems on both cars and bikes. Having to touch it means something is likely wrong elsewhere. The adjuster built inside of older breaker point type units should really be a one time setting done at the unit being brand new, then you never touch it ever again.

    Of course, one person's view only, but I have rebuilt plenty of alternators in my life and never had to do it. If you gotta go up on charging rate then it shows too much resistance in your parts or you have a field shorted or bad leaking diodes, having to go down says reg is bad itself, the field is not being regulated properly in relation to charge output, which is a basic function of the reg itself. A new field coil intentionally overwound a bit to charge more MIGHT need to be backed off a little bit on charging rate.

  8. #8
    CB750 Member chuter's Avatar
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    Received used regulator today. The cover looks like it has never been off since new. I removed it and all parts inside are super clean. reinstalled cover and installed in the bike. Made all connections and ran. Checked voltage at battery at 2000 rpm. Read 13.4. Ran up to 3000 rpm and read 14.0. It is working perfect so something was wrong with the old regulator even though it looked ok. Maybe the contacts were dirty. I'm not sure but I'm happy now. All lights are nice and bright. Thank You for the info and help, Chuter
    Last edited by chuter; 12-09-2019 at 07:24 PM. Reason: spelling

  9. #9
    CB750 Member chuter's Avatar
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    35 degrees yesterday but pretty nice and dry. Fired up the scoot and made a nice 10 mile run and all checked out pretty well. Cruising along she charges at 13- 14.5 vdc. I was pretty happy, cold but happy. Really hate to put her away. Next week it is supposed to get up into the 40's. Just might hold off for a little while longer.

  10. #10
    CB750 Guru amc49's Avatar
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    Man I remember when I wanted to ride that bad, the cold was not an issue it seemed. Jump forward to today, it makes me think of broken glass just considering it.

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