new cdi new mag and new plug still no spark

Discussion in 'Electrical' started by Dooley, Nov 27, 2013.

  1. Dooley

    Dooley New Member

    I have a skyhawk 80cc. Replaced plug,cdi,mag. Still no spark, any solutions?

  2. jaguar

    jaguar Well-Known Member

    If the spark plug cap requires that the spark plug have a nipple on it and it doesnt then that allows a gap sufficient enough that the weak standard ignition cant spark across.
    Other than that maybe you have a kill switch that is screwing up.
    If not, then its possible you bought a bad stator coil or CDI.
  3. Dooley

    Dooley New Member

    No nipple needed, checked that already. Gonna test the mag and cdi in the morning ( if I can get away from family that's in for turkey day... lol)
    The original mag was testing good but cdi wasn't. Bbought new mag anyway.
  4. Dooley

    Dooley New Member

    Ok, froze my rump off and all test show good but still no spark! HELP!!!
  5. crassius

    crassius Well-Known Member

    small break in a wire, dirty ground connection, bad kill switch, white wire touching ground, wired wrong?

    I built a CDI tester that checks strength of spark and timing of spark, but few other shops seem to have one.
  6. jaguar

    jaguar Well-Known Member

    Being an electronics technician I find it funny that people think they can properly "test" the CDI with a multimeter. Its input circuitry is a combination of diode and resistor and so it matters a lot how much voltage the multimeter is applying when a resistance test is done.
    Disconnect the CDI from the stator coil. Connect an AC voltmeter to the coil wires (blue and black). Push the bike with the spark plug removed and see how much voltage is generated. I have seen as much as 50 volts on mine. Drastically less indicates a bad coil. If the voltage is suficient then all that is left is the CDI/high-voltage-coil, assuming that the spark plug isnt screwed up.
    just to cover everything, clean off all shelac where the stator coil screws touch. Shelac would prevent good ground loop electrical current.
    Dooley and BigBlue like this.
  7. BigBlue

    BigBlue Active Member

    So that we are talking the same language, by magneto, you mean the magneto coil and not the magneto rotor? If you removed the magneto rotor, did you put it in correctly?

    Is your engine a new install or have you been riding the bike? If you been riding in the rain or left it in the rain, the magneto coil maybe ruined.

    As Jaguar stated, the kill switch may be the problem. Remove it from the circuit and try starting. Sometimes you can push it while attempting to start the engine and it will sometimes unstuck its self. I had an 48cc kill switch that would stick all the time, so I would kill the engine by popping the clutch.

    Here's how to check the ohms reading on the magneto coil:

    Set your meter to 200k:

    1. Should get 2 ohms between black and white wire.

    2. Should get 300 - 400 ohms on the blue and white wire.

    3. You should be getting 300 to 350 Ohms with the the blue and black wires.

    Here's how to check the CDI:
    Put your Ohms at 200K scale.

    1. Positive lead on Blue wire and negative on black wire should be infinite (no activity).

    2. Positive on black wire and negative on blue wire should be 130 - 150 ohms.

    3. Positive lead on spark plug wire and negative on blue wire should be about 135 - 155 ohms.

    Switch scale to 20k to check spark plug wire with black lead should be about 2.5 - 2.7k ohms.

    All are approximations for ranges.

    Also, make sure your plug is grounded against the engine when checking for spark. If not, you may damage the CDI.

    Go over your connections and make sure they are connected. I once had either the blue or black wire not fully connected, even though it appeared connected. Also, check to make sure the spark plug wire is secured to the CDI.

    I am not trying to be condescending, but don't know what skills you have and you've left out information that will help us solve your problem.

    Good Luck,

    AKA: BigBlue
    Dooley likes this.
  8. BigBlue

    BigBlue Active Member


    Thanks for the advice. This is would good for finding fault in a no-start situation. Another tool in the tool box:)

    For intermittent running problems, I wonder if you'd get 50 A/C if the magneto coil is corroded from water. My guess is that you'd get under 50 volts A/C, but as the magneto coil heats up, the voltage would drop. Would a A/C voltage test under compression be a better test? My guess is that the disparity in voltage would be greater under compression than without compression.

    AKA: BigBlue
    Dooley likes this.
  9. Dooley

    Dooley New Member

    Thanks jaguar and all.
    My background is ... I am a mechanic, motorcycles,atvs,dirt bikes,even scooters. But this lil sucker is givin me fits!!! It SEEMS too simple. Ok more information on it, no kill switch hooked up, it is taped. Black and blue from mag is hooked to black and blue on cdi. Both are new. Followed other threads and used tester, got proper readings. Never thought of using ac voltmeter... I know this can damage cdi or regulater on bigger bikes if done improperly. I do know how though. Can I use a drill to crank it over without hurting the engine ? Use this method on smaller engines.
  10. Dooley

    Dooley New Member

    Thanks big blue
    Good point about voltage dropping when it heats up.
  11. Dooley

    Dooley New Member

    Ok guys snuck away from family on turkey day. Did testing on mag and cdi.
    Mag readings: set on 200k b&w 00.1, blu&w 0, blue and black 0, sooo bad mag right?
    Ok test on cdi: pos on blue, neg on black 0, pos on black, neg on blue 145.2. Pos on plug wire neg on blue 157.6. Switch scale to 20k. Pos on plug wire neg on black 6.64
    What do i need to do?
  12. crassius

    crassius Well-Known Member

    usually, with the plug out, you can do this - I have, on occasion, seen folks strip the rotor nut when the clutch is dragging a bit - pulling the flower nut off the clutch might be a good idea
    Dooley likes this.
  13. Dooley

    Dooley New Member

    Will keep that in mind when I do it crassius. Found out I received a bad magneto.
  14. Dooley

    Dooley New Member

    I have mailed the bad magneto to the company today. will be a week or so before I get one back. Any recommendations on performance mag?
  15. Dooley

    Dooley New Member

    Are these readings right?
  16. Leroybrown420

    Leroybrown420 Member

    Has you engine ever started? If not, take off the magnetic rotor. Make sure it has a key-way. If good, flip the rotor over. I have had 2 engine straight of the the box that wold not start because the rotor was installed backwards. Also check that the mag is laying flat on the case. Many time they need to be sanded down to fit flush, a dab of dielectric grease helps too.

    Info on testing your magneto: Mystery.html

    If everything else fails, try crossing the blue and black wires.
    Dooley likes this.
  17. Dooley

    Dooley New Member

    Hey guys,
    Sorry for taking too long to get back. I own a bike shop and it is deer hunting season here. Soo.... I have been swamped with 4-wheelers. Lol. I finally received the magneto back, installed it. The bike fired right up and runs like a champ. Thanx soo much for the help.
  18. Dooley

    Dooley New Member

  19. HeadSmess

    HeadSmess Well-Known Member


    white sand. how tropical :jester:
  20. Hoo

    Hoo Guest