no spark, tried everything I know

Discussion in 'Electrical' started by MrHungwell94, May 19, 2015.

  1. MrHungwell94

    MrHungwell94 New Member

    I can't get my engine to start. The spark plug isn't sparking. I've tried replacing the coil with one from an old parts motor I have and purchased a brand new coil, cdi, and spark plug. So that's 3 coils, 2 cdi's, 2 spark plugs, and I can't even get a spark...I'm fresh out of ideas and completely desperate. What else could possibly be wrong?
     

  2. crassius

    crassius Well-Known Member

    had one once on which they'd painted the motor so badly that the head was not grounded to the rest of the case - not likely tho in your case

    I'd first load all that stuff onto the parts motor & spin that with a drill on the crank to see if it fails to spark also - might be several bad parts working against you.
     
  3. Slogger

    Slogger Member

    I'd get out the meter and check all the wiring for continuity and for a short to ground on the blue wire, and the grounding of the magneto coil. I have read some use a wire under a mounting screw while others rely on contact of the coil's iron core to the crankcase. Then there's the kill button, the meter should show an open through it.
    The kit's wiring connectors can get corroded or loose and give trouble. Check them wires.
    -good luck with it!
     
  4. MrHungwell94

    MrHungwell94 New Member

    Thanks for the tips, I'll report back next time I'm able to work on it. Not sure I'll have enough time tomorrow
     
  5. The_Aleman

    The_Aleman Active Member

    I'd double-check the plug wire where it screws into the CDI, check plug boot contacts, and end of spark plug where boot attaches.

    Some plug boots require the plug to have the screw-on resistor, some do not. Make sure you got it right regardless!
     
  6. jaguar

    jaguar Well-Known Member

    you are overlooking one very important thing- securing the ground path at the stator coil. It come shellaced from the factory and you need to remove that at the places where the 4 screw heads contact it. That is the ground path for the ignition circuit.
    If it still don't work then make sure the coil is good by measuring the voltage it is sending to the CDI.
    Also don't crimp the coil wires to the CDI wires. They have to be soldered.
     
  7. KCvale

    KCvale Motorized Bicycle Vendor

  8. MrHungwell94

    MrHungwell94 New Member

    Thanks for the help. So today I went out and bought a multimeter and determined that 2 of my 3 magnetos are junk. On the good one, the blue wire was barely hanging on by a thread so I ripped it right off. Now, I don't have a soldering iron to fix it but I am wondering, why can't I just run it off the white wire? And would simply wrapping the blue wire around its lead create a strong enough connection, or should I go out and buy myself a soldering iron?
     
  9. MrHungwell94

    MrHungwell94 New Member

    In my past builds my coil wires were always electrical taped to the CDI wires (I pull the junk connectors off the ends and wrap the loose wires together and tape them) this is the first I've heard of anyone saying to solder them. May I ask why this is so important?
    Edit: this was meant to be a reply specifically to Jaguar's post
     
  10. jaguar

    jaguar Well-Known Member

    Just coiling the wires together and then taping them means they will eventually corrode. And if they corrode enough they will break connection which can cause the stator coil to fail.

    you can't use the white wire. It has to be the blue wire. Radio Shack sells cheap soldering irons.
     
  11. crassius

    crassius Well-Known Member

    as I understand, the wire is off the mag coil - vibration is great there, so soldering is required - a quick tap with just a 100watt gun will do it (a 250watt may hurt the coil & don't forget to tin the wire first)
     
  12. Slogger

    Slogger Member

    The white wire will only have a fraction of the turns the blue wire gets around the core.
    It is about 6 volts per pulse while the blue is much higher, like 60 or 70. ( I forget) There are two separate windings on the coils with a white wire. The more turns around, the higher the voltage induced by the magnet. The white wire won't have enough juice to fire the CDI.
    I posted this just so folks get an idea of the electrical function, so they can troubleshoot more easily.
     
  13. MrHungwell94

    MrHungwell94 New Member

    I fixed the blue wire connection to the CDI ripped the white wire right off and soldered all my connections. Sure enough it fired right up and ran good for a while until I ran into other issues...they aren't electrical related though so I suppose this thread can be closed
     
  14. KCvale

    KCvale Motorized Bicycle Vendor

    I'm glad my little help page helped you.
    I think you will find your meter to be very helpful for a lot of things like if a fuse or bulb is bad or a battery or AC outlet is good.

    I don't use the stock wires on my builds.
    I put the CDI where I want it and then run a 16G double insulated wire pair from the magneto lugs...

    [​IMG]

    To just a couple of off-set pig-tail wires left on the CDI...

    [​IMG]

    Hook the kill button up there and just cap it off by epoxying a little hobby box on top.

    [​IMG]

    That little box is also a good place to put a little ignition disabling switch, in that Fito's case I used a keylock switch, but any switch small enough to fit in the box will work, just tie it in with the kill button and mag wires.

    I also always put an NGK 5944 (BPR7HIX) Pre-gapped Iridium spark plug in and a really great reliable spark is the result and sure worth it to me as a builder.
     
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