Locating Electronic problems

Discussion in '2-Stroke Engines' started by austin635, Aug 23, 2008.

  1. austin635

    austin635 New Member

    Hi everyone,
    I have had a number of problems with my new motor and have fixed all of them except for the one before me. What happens is I will engage the clutch the motor will fire no more than 10 times and then stop. Something in the electronis is causing the spark plug to quit sparking. What initially caused the problem was the two crimps that connect the blue/black wires from the coil to the CDI were touching which caused a constant short. Though now the short has caused more damage...its ruined the electronics...but I am clueless as to where the damage may be at.
    I have tested the spark plug on the outside and it seems to spark fine at low rpm's.
    Any suggestions would be great.
    Thank You

  2. dwsutton

    dwsutton Member

    I would try a new ignition module if your blue/black wires arent shorting out. That would eliminate everything else - wire, boot, module ....
  3. Skyliner70cc

    Skyliner70cc Active Member

    If you got spark, then it ain't broke. Fix up your wiring with some soldered and insulated clips.
  4. Skyliner70cc

    Skyliner70cc Active Member

    You only option is to replace parts. I'd replace the magneto first and then the CDI.
  5. BSA

    BSA Guest

    The only exception to that is if your CDI is wired incorrectly IE blue to black rather than blue to blue. it causes the plug to spark at the wrong time.

  6. BoltsMissing

    BoltsMissing Active Member

    Ok, lets leave out the electrics for now and move onto the next probable cause.., Fuel.

    It fires, then it stops...,
    Therefore we have spark..

    Will it fire up again ? if so, straight away ?

    You did say in your intro post that it's "urgent", me thinking maybe in your initial excitement, perhaps something ya missed during install, or some unseeable damage to the carb.

    Try this...start the engine with the fuel cap off.
    Will it do the same ?

    next, remove the fuel line at the carby end and check to see if the flow of fuel is ok.

    Check to see if carby is tight and all the rest of it...just feel around and see if anything else is not right.
    pics would help to see what you have done, or not done.
  7. austin635

    austin635 New Member

    I will try to get pictures up as soon as my camera is fixed.
    The thing is that it initialy fires for the first start up an d then if I try to start it up a second time after that It wont spark at all. Ill check the fuel problemas and

    post results up here shortly.
    Thank You
  8. BoltsMissing

    BoltsMissing Active Member

    That's what I was trying to get
    You may have cooked things cos the white wire has nothing to do as being part of the kill switch, lesson learnt, so don't worry too much about it. ( DON'T USE THE WHITE WIRE, yet. Tape up the end and leave it as is.)

    Get a new CDI, Magneto and depending where ya located I'm sure vendors will help ya out on this forum.
    While ya at it, may as well replace the plug lead with quality copper lead and NGK right angle plug cap. Go to an auto electrician, they may have some, 7mm or 8mm will do. If you do get some, check out the differance in the copper strands of the HT plug lead and the one supplied by an auto electrician.
    The HT is like cats whiskas and quality copper plug lead can make ya finger bleed, then ya know it's good.

    That way you have a clean sheet to start with by the time you get your new CDI and magneto delivered.
    I say this cos we assume the wires were shorting out previously, chances are, one or the other or both, is fried.
    Last edited: Aug 24, 2008
  9. duivendyk

    duivendyk Guest

    How do you know there is no spark ? ,because the engine does not run?.There may well be some other reason.If the connections are tight it is doubtful that the electricals are to blame,they either work or don't although it is possible that the CDI output coil fails, that is, arcs over at higher speeds, resulting in no spark at the plug.It's unlikely that the generator coil failed.All that happened when you shorted the coil was that it stopped the engine but that should not have damaged the coil.
  10. austin635

    austin635 New Member

    duivendyk I was actually thinking the same thing you were.
    On initial tests with the spark plug out against the engine it would spark fine at those low rpm's(hand turning the wheel to check spark) But once the higher rpms were reached (actual riding) is when it began to skip or stop sparking.
    Also when I first found out that the crimps were touching and fixed that problem the bike ran for a period of 2-3 minutes before starting to bog down and not spark. It really seems like the spark is arcing elsewhere at the high rpms.
    So instead of ordering new parts should i just take apart the CDI and try locating the problem?
  11. duivendyk

    duivendyk Guest

    I woke up in the middle of the night from a dream I had in which I solved the problem ! (This happens to me a lot).It's all become much clearer.The reason your ignition failed is that you fried a portion of the generator coil when you developed the short,this opened up the winding resulting in an open circuit to ground (the black wire).so no voltage was being applied by the blue wire to the CDI unit,therefore no spark,UNLESS you restored the connection by shorting out the open portion of the winding!!.It was pretty stupid of me not to realize this right away,anyway better late than never.I assume that the CDI unit has given up the ghost now,but that may well have been unrelated to your previous incident.I suspect that the design of the CDI is marginal (not enough margin on high voltage components,that fail over time due to gradual breakdown of insulation).The output pulse transformer is esp. vulnerable.At least we now understand the anatomy of the problem.
  12. austin635

    austin635 New Member

    I'm about to purchase a new CDI (ignition modual) but some of the vendors don't carry them from what Ive seen. Can someone please direct me to a cheap CDI unit?