Engine Trouble -no spark- troubleshooting magneto & CDI

Discussion in '2-Stroke Engines' started by gone_fishin, Apr 9, 2007.

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  1. gone_fishin

    gone_fishin Guest

    it's been getting difficult to start, we've had some humid weather, so no biggy, i thought. last night, it just quit, hasn't started since.

    ok, at first i thought the magneto got wet, so i put a space heater to it for a while...no change.

    i removed the plug, used a metal strap to ground it. pedaled, no spark.

    i wired a light-bulb to the white-wire & pedaled, it lights up. wired bulb to blue wire, not even a flicker. of course, i don't think ignition can be checked that way, just covering the bases. how can i check the blue wire for power? keep in mind i have no meter to work with.

    the key, i think: is it possible for the white wire to have power, but not the blue?

    magneto or cdi? i vote cdi...opinions? when i can afford a part, i'll only be able to afford one or the other.

  2. pianoman8t8

    pianoman8t8 Guest

    the blue and white wire are connected to the "coil" on the magneto. the black wire is a ground. So pretty much the blue wire should have power coming out of it, and to complete that circuit must go through black wire (ground), and if it doesn't, magneto is prob. fried. I had to get a new one a couple is weeks ago and it worked fine after that. I also had no spark, so i orderd a new CDI first, still no spark, so i order a new magneto from dax, and it worked fine after that. I also had a new champion spark plug, too.

  3. gone_fishin

    gone_fishin Guest


    i used alligator clips & an auto dashboard bulb & fitting.


    i get light with white/black and blue/black...yay!

    CDI is the culprit.
  4. pianoman8t8

    pianoman8t8 Guest

    nice, augie. i like your system. :D
  5. srdavo

    srdavo Active Member

    now that's thinking outside the box. nice job bro!! :)
  6. azbill

    azbill Active Member

    make sure you tell dax he told me he only ever saw 1 go bad when I was having my spark probs
  7. gone_fishin

    gone_fishin Guest

    well, i bet this one didn't go bad so much as suffer damage...sometime during the last coupla months, never could figure out what exactly happened, some insulation was worn off the wires right where they leave the cdi box, and there were a few wire strands torn also, too close to the box to do a real repair. i used some liquid electrical tape & it seemed fine, but i think the remaining wire strands finally shook loose under the repair.

    today's troubleshooting confirmed that, i'm pretty sure.
  8. gone_fishin

    gone_fishin Guest

    i got the CDI today, but i still have a problem, actually i had a few but i fixed the others.

    wired the CDI in, pulled the plug, cleaned it, gapped it to a solid .030. pedaled, it wanted to spark up briefly. it did that a few times, sputter without really firing up. ok...checked the plug, it was sopping wet.

    taped the plug to the exhaust and connected it, pedaled. very light & weak spark. i'm thinking to myself maybe it's just because it's still light outside and i couldn't see it very well, but it sure didn't look strong enough to ignite that much fuel.

    pulled the carb. first thing i found was the top tab on the carb was broken off. closer inspection proved that the edges on the clamp is what breaks the top tab. file off the little locater-nub and use a hose clamp before yours breaks, too.

    disassembled the carb. the brass float/needle bracket was pretty closed, i'm thinking maybe i'm constantly flooding it.

    this is how i adjusted my float level: turn the carb upside down, push the tickler all the way down (up), use a flatblade screwdriver to reach in & lightly spread the gap, just until the tickler will still make about 1/16" contact with the bowl. to me, that looks just about right.

    ok, let's dry everything out...plug out, carb off, clutch engaged, pedal pedal pedal. while i was doing that i reached down and put my thumb over the intake...boy, these things really draw air!! (after feeling that volume of air-intake, i knew at sea level i could go to the 3rd slot down for a good mixture, providing i can get it running at all)

    put it all back together. used some zippo lighter fluid for a quick prime before screwing the plug back in. it sparked and ran for about 5 seconds, til the real fuel hit it. which leads me to the only question i have left...

    can the magneto be intermittent or weak but still appear to be working?

    (i just had to go try it once more before i clicked "submit" :lol: )
  9. srdavo

    srdavo Active Member

    Have you tried a different sparkplug?
  10. azbill

    azbill Active Member

    intermittant problems are the hardest to solve :(
    sounds like the problem I was having tho
    mag worked when wanted to ...then not at all
  11. gone_fishin

    gone_fishin Guest

    srdavo: yes, 2 different ones, various gaps.

    'kronic...ahha, then it must be the magneto, maybe the damaged wires in my old CDI brought this on.
  12. azvinnie

    azvinnie Guest

    the mag is the prob, seen it happen first hand, you would think it would be the CDI, but it's the mag, replace it augidog and you will roll'in once again.
  13. Guest

    Guest Guest

    That was one thing that swayed me to buy a Dax engine kit. The parts are cheap. Usually a CDI is a hundred bucks, and a mag....I don't want to talk about the Fairbanks Morse mag for my brothers old Gravely!

    On the dax site, everything looked pretty inexpensive.

    Plus the 30 day warranty on parts.
  14. thatsdax

    thatsdax Guest


    Between the Black/ground and the blue lead you should get 270ohms + - 10 percent. IF you do not...Then your mag is bad.
  15. shane1234

    shane1234 Guest

    So Frustrated...no spark.

    Hello everyone. This is my first post here - I was hoping that I could solve my problem based on other people's experience. This particular thread has been quite helpful. I still have no spark though.

    Coming from my engine I have 3 wires - black, blue, and white. From the CDI I have green and black. As usual - the instructions are horrible. They say to hook up the wires to the exact color from the engine to the CDI. Yeah right - maybe if they made the wires the same color I could do that. So I've hooked up black/black and blue/green. Never sparks.

    From other posts I've heard that the spark plug boot tends to break after a few times putting it on and taking it off of the plug - mine broke first time. So I went to the local bike shop and picked up a new one. I took my CDI in too - but they said they have no way to test it. So I ask you all - is there a way to test the CDI? I've taken out the plug and hooked it up but I get no spark. Tried grounding it to the engine too - no spark. I hooked up a test LED to my magneto and peddled. It flickered on and off as I would expect.

    So - is there a way to see if electricity is coming out of the CDI? I've had this thing put together for 2 weeks now and am completely frustrated.
  16. gone_fishin

    gone_fishin Guest

    blue to green (kill switch goes here)
    black to black
    cap off the white (until you're ready to go nuts trying it for a light)
  17. Cookie

    Cookie Guest


    Aug I was having the same problem I tried to post but you know my problem......
    How meny miles do you have on Sabrina?
    on mine at about 3000 she was acting up like yours luckly I had some extra parts so I replaced the CDI that was not the problem, replaced the plug, nothing then I cleanded out the bowel and took the mag apart and it was DIRTY!! cleanded the mag out with some MEK and a drop of new greas and there where a LOT of metal shavings in there and just plane ol crud the bike was hard to start but then after choaking the hell out of her she ran like her tail was on fire the engin is geting old now and she has her own personality like an old Ford. But she has made several long runs with no problems
  18. gone_fishin

    gone_fishin Guest

    i remember that topic, cookie...yeah i tried everything mechanically logical to no avail...the humidity & corrosive sea-air (i'm literally a spit away from the pacific ocean) is gonna wreak havoc on anything it can get to.

    plus, like i said earlier, i experienced physical damage to the cdi wiring that may have been a contributing factor.
  19. gone_fishin

    gone_fishin Guest

    replaced CDI & magneto...on the road again :D

    thanks to all who helped this old soldier, you know who you are 8)
  20. srdavo

    srdavo Active Member

    good to hear, Bro. :D