Light works when bikes not running but doesn't when motor is on..

Discussion in 'Electrical' started by NSH911, Mar 19, 2016.

  1. NSH911

    NSH911 New Member

    Completely took the lights off and even when the head light gets close to the bike ( not even touching my bike) the lights start flickering all crazy, the second I pull them away, the lights work properly???

    Any help would be great! Thanks!

  2. wheelbender6

    wheelbender6 Well-Known Member

    We could use a bit more info. Is the headlight battery powered or running off the white wire?
  3. HeadSmess

    HeadSmess Well-Known Member

    its called EMI, electromagnetic interference.

    the headlight is LED. it probably has a "3 click" switch, once bright, twice, dimmer, 3 times, off... or similar :)
    that requires a digital circuit internally. 99% of LED circuits have some kind of digital nonsense inside, as an LED lights instantly, and by "pulsing" the power supply, they can be very efficient! being on for only a 1/4 of the time, taking full battery current, rather than being on 100% of the time, requiring a resistor to reduce current through LED, which just wastes battery power as heat in the resistor.

    the spark creates interference that messes with the digital circuit in headlight.

    possible cures...

    1, use ngk BR*** spark plug series, they have an internal resistor.
    2, use silicon "auto" plug wire, also contains resistor...
    3, get resistive spark plug cap/boot...

    (use of resistor reduces or "suppresses" EMI)

    4, wrap headlight in foil, make sure one part is in contact with earth or bike frame.... electrostatic shielding!
    5, wrap CDI unit in foil... same deal!
    6, place headlight AWAY from ignition systems!
    NSH911 likes this.
  4. NSH911

    NSH911 New Member

    Thank you HeadSmess. I have a ngk BP7HS 5111

    I will try foil first if that dosnt work I'll move too the pug!

    Thanks again
  5. jatgm1

    jatgm1 Member

    im having a similar problem. i bought these cheap turn signals/brake lights online, and when the engine is off their fine, but when the engine is on the blinkers dont blink, they just stay on.