Motorcycle Repair: Spark problems, honda cb 125, plug caps

Question
Hello.
All of the sudden my Honda CB 125 decided to stop ignite for me. I removed the plugs to see if i had any sparks. None found on either of the cylinders.

Now, by pure (un)luck i held the sparkplug a few millimeters away from the cylinder when i tested and realised i had a nice blue spark between the negative pole of the sparkplug and the cylinder.

What could be the reason of such behaviour? There is NO spark inside the plug, just between the negative pole and the cylinder. :o

Thankful for pointers.

Answer
Hi Daniel,

The spark plugs may be defective, plug leads may be leaking current, plug caps may be leaking current, or other.

Flash-over may occur when the spark plugs become dirty on the plug's exterior surfaces. Current may travel along a  grimey conductive surface and prevent an arc at the plug gap.

The CDI is obviously working well.

Respectfully,
Mark Shively