Electrical Problem

Discussion in 'Tech Area' started by HondoMan, Aug 2, 2019.

  1. HondoMan

    HondoMan New Member

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    Hi All,

    I need some help troubleshooting an electrical issue on a silver tag CT70. Here are the facts. Bike has likely not run in 40 years. I believe my wire harness and key switch are good. New bulbs installed everywhere and verified operating. Good battery installed. New coil from Dr ATV installed.

    I currently have no spark and i have no headlight or intrument light or high beam indicator. I think my issue is at the generator but i dont quite understand the wiring diagram. Should the Y wire coming out of the generator have power from the battery or not? Any help appreciated
     
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  3. Digginrebel

    Digginrebel Member

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    I am no expert for sure, but I connected things wrong once, which blew the fuse and then nothing. But are you sure the wiring is good? Pulled it out to see? Just eliminate the obvious first. Good luck
     
  4. Digginrebel

    Digginrebel Member

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    Have you done continuity tests?
     
  5. HondoMan

    HondoMan New Member

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    Thank You for the suggestion. Fuse is good.

    I just realized that i may not have the correct understanding of what i should be expecting to see. Do the headlight and instrument Lights run off the magneto only? (When the bike is running?) If so, i just have a spark problem.
     
  6. Digginrebel

    Digginrebel Member

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    Neutral indicator light should light up when you turn the key if wiring is good
     
  7. kirrbby

    kirrbby Well-Known Member

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    Yes.
    The motor has to be running for the headlight circuit to work.

    Do you have the CORRECT battery wire harness in there. The 2 black wires that are in the bikes main wire harness', have to be jumpered. The proper battery has the jumper as part of the battery pigtail/plug.
    If those blacks aren't connected/jumpered...no spark.
     
  8. kirrbby

    kirrbby Well-Known Member

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  9. OLD CT

    OLD CT Well-Known Member

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    You didn't mention installing new points. Are you trying to get a CT70 running with 40 to possibly 50 year old points still intact? :confused: if you didn't change them yet, you might want to do that... The original coil ain't the problem! Unless it was physically broken.
     
    #8 OLD CT, Aug 2, 2019
    Last edited: Aug 2, 2019
  10. HondoMan

    HondoMan New Member

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    Thanks for the inputs! Just to update and answer everyones questions - yes correct (original ) wire harness is installed, news points, new condenser, correct (and charged) battery.

    I have been shooting wires over the last two days i think i have found the problem. According to the wiring diagram, the generator should have a ground (to the motor body). I dont have a ground. I determined this by checking continuity from the generator yellow or green pin to the motor - no continuity!

    So my question now is WHAT makes the generator ground to the motor? I think i just need to clean that connection.
     
  11. allenp42

    allenp42 Well-Known Member

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    To answer your question, the lighting coil has a wire that connects to ground as wells as the primary coil (for spark). You should read ~1.6-1.8 ohms to ground when checking the primary coil with the points open. Green to ground is about 0.7 ohms, Yellow to ground 0.6 ohms.

    If all values check out as an open circuit, I would suspect that one of your test leads is on a rusty or corroded part on the engine.

    But to answer your question, there is a tap under each screw that is the ground for each coil.

    I've attached a pic of stator for a 77 CT70 with arrows pointing to the tabs. Please note that on most pre 77 bikes, the ground tab for the lighting coil is usually on the right side.

    You can also check yellow to green, and I hope you'll see about 1.1 to 1.3 ohms.
     

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