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Points Gap, ignition coil wiring, and static timing questions

Discussion in 'The Garage' started by TimmyT, Jun 2, 2013.

  1. TimmyT

    TimmyT XS400 Addict

    Wanted to ask these questions before its too late in the game as my bike is going to be fired up soon after rebuilding the entire thing.

    Every reference and wiring diagram I have seen for my '78 refers to the ignition coil colours as Grey being Left side ignition coil and piston and Orange being Right ignition coil and piston. Taking the points cover off and following the wires I have concluded that Orange is left and Grey is Right side and have wired them this way. I just want to verify as when I bought the bike it was actually wired as Orange/Right & Grey/Left.
    The service manual does back my thoughts that it was originally wired wrong but other info out there is conflicting. Please set me straight before I cook the harness.

    This bike does fire LEFT to RIGHT correct?

    Also wanted to mention the two wires covered in white cloth coming from the points that go directly to the wire harness, maybe I overlooked the diagram but couldnt see what this was for .... I assume the killswitch?

    Next question is the points gap...Some say this is the only adjustment needed, cant be true can it? If not its gona cost me another oil change.

    Lastly I have seen the vids on setting the timing ect. but when I was checking nothing seemed quite accurate... I made no adjustments but the points gap for now until I have more information on my above questions. Could it be possible that the wiring was wrong subsequently throwing off timing as the P/O attempted to fire it up?

    Any help, advice or comments appreciated:)
  2. drewpy

    drewpy Excess twin Top Contributor

    1) if the bike doesn't fire or backfires the connections are reversed

    2) white cloth is the points connections (that's why it is coming from the points cover)

    3) gap and timing need to be done;

    gaps should be really done via a dwell meter and timing using a timing gun.

    points are really simple things and so long as its all timed up, there should be no problems
  3. Yamaha XS360

    Yamaha XS360 XS400 New Member

    Hi there, new to the forum here and to the Yamaha XS series in general. I've been riding around on my XS360 at 30,000 miles all Summer with minimal issues, replaced the condenser, and carb but that's about it up until now.

    Now, the timing is slightly off, possibly need to reset the gaps. I know because I checked out where the needle lines up with each side. I've fixed every issue myself but I'm letting this one go to a mechanic. I have an appointment scheduled two weeks from now but I also want to keep riding while the weather is good.

    Should I hold off on riding it or should I play this safe?

    - Thanks
  4. Gra900

    Gra900 XS400 Enthusiast

    If it runs ok, ride it. Points and timing just affect how well it runs. It’s a very slow decline in performance as the points gap closes. It’s pretty straightforward to set the gap, feeler gauges and a bulb or multimeter. And timing also. Get a Haynes manual or check out the workshop manual on this forum.
    Good luck
    xschris likes this.
  5. XSLeo

    XSLeo XS400 Junkie

    Points are very simple.
    Power goes to the coil, power comes out of coil to points.
    When the points are closed current flows through the coil, this charges the coil. When the points open the current stops. Thus makes the coil spark.
    If you pull your pugs, stick a finger tip in a plug hole. Turn engine slowly. As the piston comes up on compression it will try to push your finger tip out of the plug hole.
    When this happens start to watch the timing marks and the points. One set will be closed. As the timing marks line up one set of the points will open. You will see this as the high spot on the lobe starts to move the points.
    When the timing marks line up, set the gap on the points that are just opening.
    Once set move to the other plug hole. Repeat as you did the first time. This time the other set of points will be the ones to set.
    Gra900 likes this.

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