Hi all,

my bike (enduro KTM 300 EXC) stopped running for some seconds,
then ran again. Some hours later it did it again, then again..
then stopped and never came back to life.

No spark.

I checked all the wires, they were OK, no short with each other,
no opens, all was right.

So I checked the resistance of the pickup, of the ignition coil
and of the stator (batteryless CDI), the spark plug and its cap.

All absolutely perfect.

I concluded it was the CDI damaged, and I bought a new one, and
mounted it.

But the damn spark didn't appear neither now.. =3D8-(

So what he heck!? I was going to buy a new flywheel, thinking it
may have de-magnetized, but I had one thing to test first, albeit
probably useless:

Luckily, I had an inductance meter and even more luckily, I had
previously measured and wrote down on paper the inductance of the
ignition coil's primary and secondary, of the stator and of the
pickup.

Now I measured a 30% increase of inductance in both the primary
and secondary of the ignition coil, I guessed it may be due to the
difference in temperature (that time it was cold winter, now it is
warm summer), the pickup inductance instead was practically the
same of then and, surprise surprise, the stator's inductance was
just one fourth (!) of the one I measured when the bike was working.

But the resistance is the same of then!!

Just to rule out the ignition coil, I charged a .47uF 400V capacitor
and discharged it accross the primary, and I got the magic spark.

Anyhow, I went to a friend who has a similar bike and borrowed his
stator, now my bike got back its spark!! Even with the old, and
supposedly broken, CDI. So it was the stator.. but resistance reads
OK! No false contact, absolutely..

I had to give back the stator, I'd like to repair mine, the ohms
are just right, only the mH and the voltage (as seen on the 'scope)
dropped to about 1/4.. could anybody explain me how this magic has
happened, and how to revert it please? It's just a wound wire, it
shouldn't behave like this!! :-/

Thanks,
Mario

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