Ignition - magneto wire hookup
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Thread: Ignition - magneto wire hookup

  1. #1
    Senior Member slowmod's Avatar
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    Apr 2014
    nova scotia

    Ignition - magneto wire hookup


    i am putting my '90 back together after a couple of years apart.

    can anyone tell me the correct hookup for these two wires?


    under the seat, just forward of the battery box, by the rectifier, the leads from the magneto/stator/ignition pickup coil connect to the leads from the ignition unit over by the relays.

    both leads from the pickup coil are reddish. one connector is (maybe) marked with brown paint.
    one lead from the ign unit is red, the other is brown.

    brown is the wire colour of switched +12v on the bike, which may or not be the case with this wire, but i don't want to fry stuff.

    notwithstanding potential frying, the pickup coil probably generates a weak a/c current, so polarity may not be a problem.

    the wiring diagram that came with the bike does not specify colour for the wires going to the pickup.

    anyone else have brown paint on a connector, or have experience hooking these up?


  2. #2
    Senior Member bluefox's Avatar
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    Mar 2014
    I would really look for a clean part of the wire to find the true color. Cause it looks like you do have to different color wires from the picture.
    The one with brown paint does look brown and the one from the magneto looks red. I would go and connect the like cables.
    They both according from the diagram looks to be going the same place. So may not matter but I wouldn't risk it. I have some type of flash back when it comes to the paint...kind of like mine had it too but dont quote me on that.

  3. #3
    Senior Member slowmod's Avatar
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    Apr 2014
    nova scotia
    hey thanks for the reply bluefox.

    looks like you came to the same conclusion as me - the wires probably hook up this way, and it would probably be ok even if they are crossed, but....

    the two wires from the pickup are actually a bit more red than in the picture, same as further up the wire.

    i will have the side cover off in a couple days so i will have a look as the pickup and generator windings are in the side cover.

    in the meantime here is a hopefully slightly bigger version of the picture.


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  5. #4
    Senior Member slowmod's Avatar
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    Apr 2014
    nova scotia
    picture of the same wires. again, it points to how my wires "probably" hookup.

    this indicates that there would be no smoke and sparks if they wires are crossed, though the pickup signal might be 180 deg out of phase if crossed.

    "GoNOW wrote:
    Nope. It's a pure short to ground system. On the TW and many bikes of that era, they had separate charge coils for the cdi. They don't use battery power at all to make spark. 12V never goes to the cdi."


  6. #5
    Senior Member slowmod's Avatar
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    Apr 2014
    nova scotia
    so the brown and red wires are actually the "source coil", which supplies power directly to and only to the cdi
    (and maybe via the cdi to the ign/spark coil).

    the green and white wires are the "pickup coil" that tells the cdi when to fire.

    the yellow, white, and black wires are the "charging coil" aka "stator", which charges the battery / runs lights.
    (black is a direct ground from the stator.)


    i looked closer at my red/brown connections and there is a slight variance in the wire colours; the supposed brown wire has the supposed brown paint on the connector; and also a blue mark that matches up with a blue mark on the brown connector from the cdi.

    so i'll be good to go based on all that, but here is what should be a definitive test:
    (if anyone feels like verifying this on a working bike, that would be great).

    according to the service manual at

    the source coil actually has two windings, with 3 connections, the 3rd being ground.

    the manual only gives "400 -450 ohms at 20 deg c between brown to red" as the test.
    it does not list a measurement between each wire and ground.

    i metered mine (at about 5 deg c) and this is what got:

    red ^^^^^^^^ brown ^^^^ ground
    |________________________________| ~ 415 ohms (red to ground)
    . .............................. |_____________| ~ 29 ohms (brown to ground)

    so that's a pretty clear identifier if you have a meter, the brown wire has much less resistance to ground.

    given the difference in the two windings, crossed wires and (attempting?) to run the bike, would probably be supplying way wrong power to the cdi, not good.

    Last edited by slowmod; 05-01-2014 at 07:20 PM.

  7. #6
    Super Moderator goldenhtr's Avatar
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    elkraken likes this.
    A very very wise man once said “it’s more fun to ride a slow bike fast, than a fast bike slow”.

    "Now then get your weapons... and go out to the open country to hunt some wild game for me"

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