Engine Trouble Engine stopped running, think its CDI, need advice

Discussion in '2-Stroke Engines' started by scubaru89, Oct 1, 2012.

  1. scubaru89

    scubaru89 Member

    So I rode my bike to work which is a 4 mile commute, all was well. When I went to drive back home some hours later I must have made it half a mile and it stopped working. Through a few attempts I could tell I flooded the engine so I had to pedal back home.

    Took the spark plug out, removed the carb, let it dry out the cylinder, and then I started taking things apart to check for problems and found this in my spark plug boot.

    http://i776.photobucket.com/albums/yy49/subaru_steve/Motored Bike/PhotoSep3075942PM.jpg

    I replaced the whole boot/wire today and its still not firing. I rest the spark plug on the cylinder and pushed the bike looking for a spark but saw nothing. The guys at Bikeberry told me to hook an ohm meter up to the two wires and look for 6-8 ohms of resistance which I have yet to do.

    The bike has been running fine for the past two weeks, the thing that may have caused this was 3 days ago I had to ride home in the rain (a light rain), I think some may have got into the CDI and spark plug boot and caused the issues.

    Anyone able to recommend a better CDI or place I could easily get one (Napa, Tractor Supply, Lowes)?

  2. BigBlue

    BigBlue Active Member

    No such replacement other than the Jaguar CDI. You may have got the magneto wet which may cause some problems. Here's a post from another member with the same problem as yours: http://www.motoredbikes.com/showthread.php?37834-wet-magneto-no-spark

    Here's a handy guide on how to check your electrical system from forum member AI.Fisherman:


    Good Luck,

    AKA: BigBlue
  3. scubaru89

    scubaru89 Member

    So I got ahold of a multimeter again and ran the measurements as described in AI.Fisherman's post.

    Magneto Check:

    Black/White----2 Ohms----------2.5 Ohms----------200

    Blue/White-----300-400 ohms---NULL---------------ALL

    CDI Check:


    -Blue/+Black---130-150K ohms---.149----------------2M

    +Plug/-Blue-----135-155K ohms---.161---------------2M

    Plug/Black------2.5-2.7 K-----------7.6----------------20K

    So I'll be honest I'm not great with understanding resistance and everything. From what it looks like I have an issue with my magneto and CDI?

    Bikeberry.com also has a video that shows how to get basic readings from the Magneto and CDI.


    Target: 327-345 OMS

    Measured: 0


    Target: 6-8 OMS

    Measured: .577 (5.77) OMS

    So given these simpler tests, looks like its my Magneto!

    Can anyone confirm or deny these results?
    Last edited: Oct 1, 2012
  4. crassius

    crassius Well-Known Member

    Yes, that's a bad magneto reading, but it may not be dead. The blue-black reading should be about 350ohms, but it is important to also check right at the coil in case of bad connections. Put the meter probe right on the tab where the blue wire is soldered to the coil, then put the other probe on the solder joint where the coil wire goes to the armature and dig it in a bit into the solder to be sure of a good connection. If this gives you a proper reading, then re-solder and then recheck at the wire connectors outside the magneto.

    Otherwise, a bit of water in the magneto case has killed your coil.
  5. scubaru89

    scubaru89 Member

    I have the Magneto free from the bike. I've had the probes on the wire, metal tabs, and as far back to the coil as I would find safe, nada.

    http://i776.photobucket.com/albums/yy49/subaru_steve/Motored Bike/PhotoOct02125225PM.jpg

    I noticed on the back of the coil the material they wrap it in had some oil on it, my exhaust was dripping some gas/oil cause I was playing with the carb settings and had it running too rich. I think the gas/oil got in and eroded some of the coil.

    Well Bikeberry is sending me a new magneto and I'll be sending this one back to them to take a look at for the warrenty. I guess this means I now have some time to work on installing my HIDs and tail light :)