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1979 XS400f wiring issues

Discussion in 'The Garage' started by William W, Nov 27, 2021.

  1. William W

    William W XS400 New Member

    Hey XS’ers. I’ve read a few threads on some similar issues from others, but I’m not quite finding the answers I need.

    I’ve got a 1979 XS400f that I am turning into a brat style. I’ve done a lot of upgrades, including the motogadget M unit blue, motogadget gauges, and a solid state regulator/rectifier.

    I’ve attached a PDF here from Revival Cycles, showing the wiring diagram for the Type A charging system.
    …the three white wires coming from the ac generator are connected to the three white wires from the reg/rec.
    …I have the black and white wires connected to the green and black wires which I believe are coming from the field coils of the bike.
    …the red/white wire of the reg/rec is connected to the battery via a fuse.
    …the green wire of the reg/rec is grounded.
    …the black wire of the reg/rec is going to the output of my m unit.

    Problem 1: the charging system does not appear to be working with this configuration. The bike is running.

    Problem 2: I can’t get either the neutral light or oil pressure light to work. I’ve replaced both the neutral switch and the oil pressure sending unit. I have these directly connected to the input of the motogadget indicator lights.

    Help appreciated.

    Attached Files:

  2. BBS360

    BBS360 XS400 Guru Top Contributor

    The fact that on their website Revival lists all years of xs400s as Type A charging systems makes me wonder about them, since Yamaha changed types around 79/80.

    Changing the bike from A to B, or vice versa, isn't too difficult. Just need to switch whether the black wire in the regulator connector goes to ground or brown/+12V.

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