no spark

Discussion in 'General Questions' started by motorpsycho, Aug 27, 2009.

  1. motorpsycho

    motorpsycho Active Member

    I rode my bike on saturday and it ran great. I rode it again on monday and it ran fine and then the engine just died while riding. I could not get it to re-start. (i have the 50 c.c. japanese slant head motor).
    i thought it might be a fuel issue, so i drained the gas, and put fresh gas in (i thought maybe the mixture was off and that there might have been too much oil in the gas). That didn't help.
    so i started checking things and i found that the spark plug will only spark intermittently as i spin the back wheel. it will spark for about 5 revolutions of the rear wheel, and then the spark stops. i can spin the back wheel about 10 times and no spark...then all of the sudden it will spark once or twice, and go away again. i checked for power at the mag and there is plenty of power there. I have no way to check the cdi box, but i am wondering if anyone else has had this problem, and IF the cdi boxes are known for going bad like this.
    my bike only has about 10 miles on it and it has always started quick and ran great up until now. I have no way of testing the cdi box other than putting a spark plug on the plug wire, spinning the rear wheel and watching for spark. It's like the cdi box can't store enough energy to fire the plug all the time. even tho i get spark sometimes, the engine makes no attempt to start...like the spark is to weak when it is there. I don't see any wires that could be grouding out on anything and all of my wires have been soldered and heat shrunk. it's just weird that i get spark only sometimes and i am wondering if the cdi box actually stores voltage, or if it just bosts the voltage from the mag. does anyone know?
    all of the things i have checked are leading me to the cdi box, but i have no way to actually test it to see how much voltage it's putting out.
    i did try a new spark plug too and i get the same results. i am getting raw gas coming out of the exhaust, so that tells me that there is no spark, or the spark that is there is too weak to fire the gas.
    has anyone delt with this before?
    My bike does have a 6 volt headlight that is hooked directly to the white wire, and the headlight works when i am trying to start the motor....so there is power there as well.
     

  2. srdavo

    srdavo Active Member

    Japanese??

    have you tried disconnecting your headlight & checking for spark or attempting to start your engine?
    Your headlight could be drawing power away from your sparkplug.

    Also...have you changed your sparkplug boot & wire, to a regular automotive type? The plug wire unscrews from the CDI box.
     
  3. motorpsycho

    motorpsycho Active Member

    i meant chinese not japanese.
    no, i didn't change the spark plug boot and wire, they are still the originals.
    the headlight has been on my bike for about 2 weeks and it's always ran fine.
    but i will try disconnecting the light to see if there is any difference.
    but i would think that if the light was drawing too much, it would have done this from the day i put the light on.
     
  4. motorpsycho

    motorpsycho Active Member

    thanks for the suggestion srdavo. as soon as i got home from work this afternoon, i pulled the wire off for the headlight. the motor started right up with it unhooked. i have come to the conclusion that the headlight is shorting to ground as soon as i hook the power wire to it, and it's killing the power from the mag. which is shorting the cdi (same as pushing the kill switch) i also have a tail light that is hooked to the white wire and it's grounded to the sissy bar...the tail light still works fine and has no effect on the engine. the head and tail lights both have the same size bulbs and they are 6 volt, 3 watt bulbs.
    the headlight is grounded to the handlebar stem (the headlight gets it's ground from when you mount it, there is no ground wire) and i am wondering if this is part of the problem. i did not try grounding the headlight somewhere else...i just removed the head and tail lights, and i'll have to come up with something better.
     
  5. srdavo

    srdavo Active Member

    you are welcome. Glad you are rolling again!!
     
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