Magento Coil Wiring low Spark

Discussion in 'Electrical' started by AgusBarcia, Aug 13, 2016.

  1. AgusBarcia

    AgusBarcia New Member

    First of all, my name is Agustin, and im from Uruguay, i bought a used bike, and i cant get it to run.
    I have compression, spark and fuel, but cant start the bicycle.
    But the spark i think is kinda weak, i was reading about the grounds of the coil in the magneto.
    My coil has two wires, green and black, wich i connected to the CDI, black to black, and blue to green. That way i do get some park on the plug, but also there is some spark on the red part i draw.

    The thing is that everywhere i see wiring diagrams, people have three wires, and dont use the white one wich i dont have. Also they use a BLUE and GND to the CDI. If i do use the upper one (green) and GND, i cant get spark.

    Should i get a new one? Or is there any way i can check it to see the internal wiring

    When i put it in Ohms in the multimeter, it goes to 0. Doesnt matter if i get it on 20k or 200k.
     

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  2. jaguar

    jaguar Well-Known Member

    20K is 20,000
    so a reading of 500 ohms would deflect the needle only 1/40th of full scale.
    Disconnect the CDI from the coil and put the meter on the coil wires. Put on AC 50-100v and take the spark plug out and turn the engine over and see if it shows 30 volts. If not then replace it.
     
  3. AgusBarcia

    AgusBarcia New Member

    Ok, 10 volts, pedaling slow, and 20v pedaling faster.

    So, i guess ill replace the coil then.
     
  4. crassius

    crassius Well-Known Member

    that part where you drew red is where the ground wire of the coil is soldered to the steel of the armature - when it sparks there, it is not soldered tight - sometimes one can clean that wire and the spot it attaches to with a tiny file and solder it again
     
  5. AgusBarcia

    AgusBarcia New Member

    So i cleaned it, and couldnt find any parts soldered to the main metal part. Also de plastic is damaged, i think there is no way i could fix this one.
     

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  6. crassius

    crassius Well-Known Member

    yes, looks like a spot there on the corner where it was soldered, but sparking over time may have completely burned the wire away - best to just replace it
     
  7. Tom Ream

    Tom Ream New Member

    Carefully use the tip of a soldeing iron to cut away the plastic insulator by that broken wire, Do not damage the coil under the plastic cover. scrape off the coating on the wire stub to expose the copper. Pre tin the wire end. Lay a small pice of small gauge jumper wire, like from a telephone wire or cat5 com cable like 24 awg, no insulation pre tinned. Lay it across the old solder on the frame and the wire end and solder this back together, Test it. Once you are sure it is fixed. cover the repair and the exposed coil windings with epoxy. Like 5 minuet epoxy or acid free RTV.
    There is also such a thing as electrically conductive adhesive that can be used to repair broken circuit boars that could be used to mend a broken connection such as this.
    Rusty
     
  8. AgusBarcia

    AgusBarcia New Member

    There is no solder visible on the frame, there are no wires going to the frame, i saw some pics on the forum, but on this one i cant see it.
     
  9. Tom Ream

    Tom Ream New Member

    Hmm. I guess a new unit is in order. Curious.
    Rusty
     
  10. AgusBarcia

    AgusBarcia New Member

    So, update. Got a new coil, and volts went from 10v to 70v.
    Got it to start with choke on, but as soon as i remove it, the bike dies, so im gona re check tomorow for leaks on the intake and carb.
    So, thanks for the help, and im gonna see if i can get it to idle.
    If the bike dies with choke of, means its leaning out, right?
     

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  11. jaguar

    jaguar Well-Known Member

    check for trash blocking the main jet or the intake valve to the float bowl
     
  12. AgusBarcia

    AgusBarcia New Member

    Its, got a chinese carb, brand KNG.
    When cold it starts with choke and dies after some seconds. Then i start it with no choke, but have to use the accelerator to get it going. It revs high, and then dies if i drop the acclerator, its like or it dies, or it revs high. Cant get it to idle.
    All the gaskets are old, i know the exhaust one is leaking, so pretty sure the intake is also. Gonna check them tomorrow, does the syntoms feel like an intake leak? Also i have no idea what jet this carb has.
     

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