What causes small spark??

Discussion in 'Tech Area' started by 85CTrider, Jul 11, 2019.

  1. 85CTrider

    85CTrider Member

    Aug 11, 2009
    Likes Received:
    I get a small spark i can see when holding plug against engine.. it wont start the bike or even make sounds of wanting to start... what causes a small tiny spark that wont ignite gas i squeeze into plug hole??? is this a points problem or a bad plug problem? plug was black as charcoal when i took it out.. was a new plug... or could this be condenser i just put in?? i checked all connections.. no bad grounds.. re soldered it 3 times with same issue...
    what could it be??
  3. OLD CT

    OLD CT Well-Known Member

    May 15, 2006
    Likes Received:
    It could be a weak spark because of the plug being fouled. You may have incorrect carb settings and worn points also. Any of these issues will cause a fouled plug. Best to install new points if you can't remember when they were replaced last... I am going thru the same issue, I just raised the clip adjustment on the needle to the leanest setting to see if there is a change. Also make sure the air/fuel screw is properly set, remember if it is incorrectly set you can foul a plug ''idling'' too long.
  4. racerx

    racerx Administrator
    Staff Member Administrator

    Jul 10, 2005
    Likes Received:
    Fouled plug is the most common cause of weak spark, by far. It isn't the only one, though. Fouled point contacts (it only takes minuscule amount of oil, or rust), failed/failing condenser, bad ground (usually at the HT coil mounts) or, rarely, a dying coil. Start with the easy & common stuff first...new plug, point cleaning & gapping.

Share This Page