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  • Help with an electrical diagnosis?

    Here's a short recap of my other thread with further info below...

    I've got an XS that will not fire. Last season cylinder 3 would cease firing from time to time, but only intermittently. This year on starting it up for the spring I found neither #2 and #3 would start at all, so i took the seat and tank off to go over the connectors and look for any obvious problems. I also charged the battery overnight. Not having found any issues I put it back together in the hopes the fresh battery would magically help somehow. Sadly, none of the cylinders fire now.

    The engine is definitely getting fuel, cranking it too much without starting causes flooding all over the place.

    The engine is not getting fire at all. when I take a plug out and ground it on the side of the engine and crank it's stone cold with no spark.

    Last night I took the tank, seat etc off and went over all the connectors I could find and gave them a bit of WD40 and made sure they were actually connected properly. I also rechecked all the fuses which not only appear fine, but read continuous when using a multimeter.

    Following one of the guides in the repair pages of this site I also used the multimeter to check the resistance on several wires.

    I pulled the smaller plug off the ignition unit (the one with four wires) an checked the resistance between the yellow/green and yellow/red, then between the white/green and the white/red. Both gave somewhere around 700 to 750 ohms. I believe this is ok. I did not remove the side cover and rotate the ignition advance unit back and forth while doing this test for lack of time.

    The guide I read said to check the "resistance btween the plug wire caps for each coil" which i took to mean from plug cap 1 to plug cap 4 and from plug cap 2 to plug cap 3. I removed 1 and 4 from the spark plugs and checked the resistance and got something in the area of 27K ohms or so. Same for 2 and 3.

    I then checked the red/white wire that runs from the ignition unit to the coil that lives under the gas tank, and also the orange wire, and the grey wire that from along the same route. These would give variable readings of .4 ohms, sometimes .2 ohms, once in awhile 0 ohms. Wiggling the probes around would causes spikes as the tips rubbed the metal but I could not reliably find a spot that game a consistent reading.

    I presume this last bit is the issue? .2 ohms along the wire that carries electric from the ignition unit to the coils under the tanks sounds wrong.

    If any of the above makes no sense, let me know... I'm an artist not a mechanic and although I've been riding for 20+ years I'm never been great with anything mechanical.

    Any thoughts would be appreciated.

    datter
    Rebuilt 1981 XS1100 H
    My story

  • #2
    datter, have you checked the ballast resistor? If it checks OK (1.5 ohms), then I'd say that you need the 'solder fix' inside the TCI. Do a search here for the method. If soldering frightens you, I will do it for a small charge, PM me.

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    • #3
      The ballast resistor is located under the gas tank someplace correct? I've heard mention f it, but haven't checked it as I wasn't sure what to check for.
      Rebuilt 1981 XS1100 H
      My story

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      • #4
        It is on the left side under the tank just below the rubber isolator for the tank.
        Ernie
        79XS1100SF (no longer naked, now a bagger)
        (Improving with age, the bike that is)

        Comment


        • #5
          Re: Help with an electrical diagnosis?

          Originally posted by datter
          I did not remove the side cover and rotate the ignition advance unit back and forth while doing this test for lack of time.
          Until you test the pick-up coil wires by vigorously pulling at them to look for breaks inside the insulation, you will not be able to eliminate this as a possible source of all your problems. You don't need a meter for this either, just pull with considerable force on each of the wires. If something does pull apart, it was broken/weak to start with - there is no danger of pulling apart a good wire.
          Ken Talbot

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          • #6
            Hey Egsols,

            Datter has an 81H, so it doesn't have a ballast resistor!

            Hey Datter, okay, just want to make sure that the wires you were checking were JUST connected to the ignition coils. The Red/white wire and either the ORANGE or the Grey. You want them connected to the coils, but unplugged from the wiring harness! IF you were getting values that LOW, then the coils are probably fried! Should be 2.5 to 3 ohms!

            With the same connectors unplugged, you can use a VOLTMETER to test the red/white wire to ensure that you're seeing 12 volts coming from that wire to ground...any ground! As long as you're seeing 12 volts, AND those resistance values for the PRIMARY wires of the coils are that LOW, then you will need to replace the main coils!

            Have you seen the MikesXS coils upgrade tech tip, fairly easy to do, and quite cheap!
            T.C.
            T. C. Gresham
            81SH "Godzilla" . . .1179cc super-rat.
            79SF "The Teacher" . . .basket case!
            History shows again and again,
            How nature points out the folly of men!

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            • #7
              Right, TC, 81, 4RO TCI, no ballast resistor. Between coil wires red/white and grey should be 3 ohms. Same between red/white and orange. I read that he was testing the wires from the TCI to the coils, which would read zero ohms.

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              • #8
                Next time I'll check out the year before I ramble!!!
                Ernie
                79XS1100SF (no longer naked, now a bagger)
                (Improving with age, the bike that is)

                Comment

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