No Spark at Left Points on CB 350K3
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Thread: No Spark at Left Points on CB 350K3

  1. #1
    Senior Member dmoore2222's Avatar
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    No Spark at Left Points on CB 350K3

    Greetings All. I have a 1971 CB 350K3 that recently started running a little uneven. Since it had been six years since I cleaned the carbs I figured it must be that. So I cleaned them thoroughly.
    Now there’s a strong blue spark at the right points but no spark at all at the left points. Prior to this the bike ran smooth as silk and I haven’t done anything but change oil over the last five years. So it’s not like I messed something up while wrenching.

    Here’s what has been covered thus far:

    -Brand new battery (2 weeks old)
    -New condenser
    -New points wires and connectors
    -Both primary coils test out at 4.5 ohms
    -Both secondary coils test out at 9.7 K-ohms
    -There is continuity in the points wires from coils to points
    -There’s continuity from the points base to the contacts
    -Both points gaps are snug at .016”
    -All points mounting screws are tight
    -The points plate screws are tight

    There’s nothing I can see that would be causing a short at the left points
    I switched over the primary coil wires to the points to see if the left side would fire. It didn’t but the right side still did. Given that both coils tested good it would appear that the left points are dead for some reason which is beyond me. Any ideas would be greatly appreciated.

    Thanks. D

  2. #2
    Super Moderator J-T's Avatar
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    I hope you meant you have a strong spark at the right spark plug. There should not be a bright blue spark at the points.
    JT
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  3. #3
    Senior Member dmoore2222's Avatar
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    Ooops. I meant bright not blue. Sorry.

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  5. #4
    Senior Member ancientdad's Avatar
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    Pictures of your points plate and wires might help us see something... good close-ups that will zoom, but that is a bit unusual as generally things that worked last time usually work the next time, especially something like points that are as simple as they are. Since it's been sitting, did you clean both sets of points? If so, are you sure there's no residue from what you may have used to clean them, like a tiny bit of paper or some solvent residue if you sprayed them with something? Just throwing out some thoughts in lieu of pictures
    Tom

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  6. #5
    Senior Member dmoore2222's Avatar
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    Yes. I used some fine grit emery paper. No solvent. I'll take some close up pics. I find it odd too that this happened. The bike ran great and would start up easily. Weird.

  7. #6
    Senior Member ancientdad's Avatar
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    So, did you wipe through the points after the emery paper with some clean paper to remove any possible grit that could cause this? Or blow the points out with compressed air? It's a long shot, but I've seen it happen
    Tom

    Ride along at the drag strip - https://www.youtube.com/watch?v=20jFPazXlvU



    running points... because I'm too old for mysteries that begin with pushing

  8. #7
    Senior Member mike in idaho's Avatar
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    With the power on and the points open, you should have battery voltage at the points wire connection.Short the movable point to ground with a screwdriver and there should be a spark. If no spark remove the wire from the points and touch it to ground.
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  9. #8
    Senior Member Bill H's Avatar
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    You might try removing the points plate with the points mounted on the plate. use your meter to test continuity between the mounting screw where the coil connects and the plate if you get a reading then open the points and you should not get a reading. if you do the points are shorting to the plate. If no reading the points are ok. Check the voltage from the - side of the coil to the the connector that mounts to the points. If you have 12 volts then put the points plate back on. If still no spark your shorting to the points plate.

    Just some thoughts.

    Bill

  10. #9
    Senior Member dmoore2222's Avatar
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    thanks, Mike. I'll give it a try.

  11. #10
    Senior Member dmoore2222's Avatar
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    Sounds good. Thanks, Bill.

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