No spark, trying to troubleshoot CDI or Magneto

Discussion in '2-Stroke Engines' started by relaxxx, May 20, 2009.

  1. relaxxx

    relaxxx Member

    The first thing I did was try a new plug, no spark.
    I tested magneto wires, 330 ohms between black and blue. 2.5 between black and white. This seems to be on par with a good magneto.

    I can't find any readings on the CDI between black and blue, nothing readable testing the screw side, numbers jump like trying to read a capacitor.

    I read there was supposed to be 75V AC output on magneto black and blue wires. I could only read about 12V rolling the bike forward a couple feet. Not sure if this means It's bad or my digital meter just isn't accurate or if I'm even testing it right because it's just a quick pulse? I did hook some LED lights to the black and white and they did flash when motor turned. Also hooked same LED's to black and blue and LED's flashed very bright.

    Is there any test I can do with the CDI? Should I just bite it and order both replacement parts?
     
    Last edited: May 20, 2009

  2. Junster

    Junster Member

    Have you really checked out the plug wire? Try unscrewing it from the cdi and using a automotive wire. Just cut it off clean and push hard as you screw the new plug wire in. Then put the little screw cap back on the plug so it hooks up to the auto style wire. Leave the white wire disconnected till you get it going again. Hope this helped.

    P1010109.jpg
     
  3. duivendyk

    duivendyk Guest

    Moving bike back&forth does not prove much, you are getting an output, your blue/blk coil output is OK I think ,Digital meters use sampling this gives erratic readings on fast pulses.If there is some one out there with a multimeter and this type of CDI that WORKS plse measure between plug wire and ground (black). and report.I would expect between 2-10k Ohm.Then you will be able to compare.
     
  4. relaxxx

    relaxxx Member

    The plug wire is good. I went ahead and ordered a new CDI as this seems to be the most likely culprit. The cheapest I could find was on ebay # 400050335654, it has a green wire instead of blue. Hopefully it will last more than one season. I was just starting to ride again, now I have to wait a week or two.
     
  5. spad4me

    spad4me Member

    I have a question?
    Did you look in the magneto case to make sure it is DRY???
     
  6. duivendyk

    duivendyk Guest

    Just for curiosity's sake ,do you happen to remember what it read on the plug connection?
     
  7. relaxxx

    relaxxx Member

    I did look inside the magneto, I first thought the black wire was shorted but after opening the case i realized it's bolted right to the case so black is ground, Nice and dry inside. Plug wire was like 0.5 ohms.
     
  8. duivendyk

    duivendyk Guest

    I meant from plug connection at the plug cap to ground (black) at the CD unit, not from one end of plug wire to the other.
     
  9. relaxxx

    relaxxx Member

    Oh, I couldn't get a reading, numbers jumping all over the place. Is it supposed to be a certain resistance?
     
  10. relaxxx

    relaxxx Member

    Well I got my replacement CDI. hooked it up and still no spark. I thought I saw the tiniest spark while rolling fast but it's kind of hard to tell when the only way to test is holding the spark plug against the motor while running beside it like an idiot.

    I guess the only thing left to do is replace the magneto. Kissing goodbye another $30 and week of riding!
     
  11. linnix13

    linnix13 Banned

    wow thats the nicest looking set up i have seen!
     
  12. Stink Bike

    Stink Bike Member

    I had a similar problem and it was a faulty kill switch.You could try bypassing it.
     
  13. Junster

    Junster Member

    Thanks linnix13. Ok relaxxx first make sure the ground (black) is getting good ground to the engine. Disconnect the white wire completely. Look over the white wire to make sure it isn't grounding to anything. Then take out the plug and get the bike with the rear wheel off the ground so you can turn the engine over easily. Take off the generator cover. Make sure the magnet wheel is spinning with the motor and make sure it is not contacting the generator frame when it's turning. It needs to be very close but never touching. Check the blue wire for output it's a pretty high voltage. Also check the cover wrapping on the generator coils. Look for a stray wire sticking out. Good Luck
     
  14. duivendyk

    duivendyk Guest

    Mysterious,looks like there might be a short on gen. coil, if you have diode and electrolytic cap make up negative going peak rectifier on WW,should read neg 15-20V to ground.
     
  15. relaxxx

    relaxxx Member

    Thanks for the ideas, raising the rear wheel was a big help, I cranked the motor as fast as I could and my digital meter read around 80V AC on the black and blue wires. I could clearly see a spark this time so it's possible I just wasn't pushing the motor fast enough before. Both CDI's spark the same. I tried to start the motor and still no go. I had compression, I had spark and I had gas because unburned gas was dripping from the muffler. I though maybe I had bad gas, unscrewed the bowl from the carb and burned the gas inside. Then I cleaned the bowl, put it back and together and this time it fired right up. So I guess it was the carb all along.
     
  16. Junster

    Junster Member

    Glad you got it running again..
     
  17. relaxxx

    relaxxx Member

    It's running but to very good. Doesn't have the power it used to. and running quite rough. The fact that I don't see a spark when turning slow concerns me. There should be a spark every revolution I would think. This would explain rough running at slow speeds. Still wondering if I should replace magneto.
     
  18. stealthc9

    stealthc9 Member

    so your carb was to blame?? and what type of petcock is that? it looks nice ur set up is very clean.
     
  19. Junster

    Junster Member

    relaxxx check your headbolts. Your motor is getting just to the point they may need a little tightening. Not to much though. Oh and stealthc9 if your talking about the pic I posted that's my bike. The blue handle petcock is from Sick Bike Parts. It's $9.95 and totally worth it. Really high quality ball valve.
     
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