dead CDI (maybe)
 

Started loosing spark, while in the bush.
Flexing HT cable, checking sparkplug, all got flawless, idling, acc, revving. Did the whole training and got home.

Last ride, same story, 5 minutes after startup. When it cut, it did completely.
Pushed home..
Since, 've sanded coil contacts, tested other coil from moped, tested HT cable, cap and sparkplug resistance. Spark returned, lets ride, but it stalled again, and no spark since.

Lighting works.

So, beside pickup coil, stator and wiring loom there is an option that CDI gave up.

I read that suzuki 125 CDI's fit, but do RM 250s also fit? I can get a hand on '06 cdi, or try fitting mine on this bike, just to check if suzy gives the spark with my CDI.

I also have no reference values to measure electronics on this bike, like real workshop manual. It's not downloadable from parent side.

I don't want to throw you off your course on this, but I had similar issues recently on my 2014. This may or may not apply.
In the end what fixed it was tightening the CDI connector pins. I had to replace one that I squished too far accidently while trying to make the fit tighter. It produced some strange symptoms including intermittent spark.

Here's my thread
http://www.gasgasrider.org/forum/showthread.php?t=21524

Ok, so you removed all fittings from the wire connector, that attaches to CDI, and you gave them a little squeeze, for better contact with CDI pins.

Should be able to test the cdi with a voltmeter.
somebody has those numbers somewhere.

Correct, I had connectivity problems with 2 pins. The first was the CDI power supply, the second was from the pickup coil.
Use caution if you do play wit the connector / pins, they are quite fragile. I ended up damaging one, and had to borrow a replacement from the dual ign map wiring.

What year is your bike? I have an one from my '05 250xc I could send you to test...

I had a similar prob that turned out to be a problem with the kill switch! cleaned it all up, works fine now!

Thanks guys, bike as per signaure.

Tested CDI in suzuki rm 125, working, so it showed I had wiring problem.

Had no time to ride, but got consistent spark, by brake cleaning and blow drying both connectors and removing the seal.

It seems like silicone seal had increased in size or lost its tightness, not allowing the connector to be pressed in fuly, even though the click engaged.

Well, I was wrong.
After 7klms transfer to local track, not even finished warmup lap, doing first bigger rev and it cut out again, had to bo towed home.

I'd really like to get some values to measure all components, and I'll test all the wiring, which looks like a partial mess.