How do you know if your CDI is bad
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  1. #1
    Member Lido's Avatar
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    Hey Folks! This is probably a very stupid question but how do you know if your CDI is bad? What will or won't happen? Just wondering! I have a 1987 and it has a bad reputation for having CDI problems. It's like I'm just waiting for the CDI to go. But I don't know what to look for.

  2. #2
    Banned qwerty's Avatar
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    Look for a new CDI. No longer available from Yamaha for '87s. Better yet, look for a '01+ complete electrical system. Might as well go for the automatic cam chain tenseioner, too. Then you'll have the best of both versions: H4 headlight, dependable electrics, and a kick start.




  3. #3
    Senior Member lizrdbrth's Avatar
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    In my experience they either fail totally (no spark) or intermittently.



    The intermittent failures are generally loss of power at top end due to loss of spark advance, or intermittent misfiring. They'll run, but they'll run like crap or run fine for a period of time, then shut down, only to restart a few minutes later. This can be difficult to diagnose, generally resulting in at least two carb cleanings/rebuildings, several trips in here to ask questions and shop for easy answers before biting the bullet and actually looking for the problem step-by-step, and you being really frustrated and hating myself and others for not telling you what you wanted to hear



    If and when your '87 begins to display these symptoms do yourself a favor and axe me about my timing light, which will save you from all of the above.



    Meanwhile, ride the snot out of it, maintain it and quit waiting for the other shoe to fall.



    We have a few really smart folks in here working on alternatives, and I have little doubt they'll come up with alternatives shortly.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  5. #4
    Senior Member operose's Avatar
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    I have crawled around the sewers of the internet with a magnifying glass, and have found at least 9 documented cases of "top end loss due to failed CDI" -- the bikes were a healthy mix of 1987 models as well as 88-97. Many others were found that either failed completely or the person did not come back to inform the internet of the resolution.





    If it works right now, just keep running it. If you do find a good deal on one it would be smart to pick it up for the future, but not necessary to continue riding for sure.
    ITCB

  6. #5
    Member Lido's Avatar
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    But is it like a milage thing that once they get up there on miles? Is it a weather thing like if water and dirt gets in them? What is the cause or main cause of them going bad?

  7. #6
    Senior Member operose's Avatar
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    It depends on what inside them actually fails. Hilariously enough, after all the research put into this, I am still not sure what component actually gives up the ghost in a situation like mine.



    Chances are if it completely "fails" as in the bike won't run at all but will with a different CDI, there is a wire or connection broken. This would probably be the easiest to fix, as you can open it up and resolder whatever connection needs it.



    If the thing is running poorly (loss of top-end power) as a result of the CDI, it is something inside the timing circuit that has failed.



    They can of course also "fail" (like most electronic devices) due to age, voltage/amperage spikes, corrosion due to water, etc.
    ITCB

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