MZ ETZ 250 randomly shutting off

[Kruh]

I have a late model ETZ 250 with an original electronic ignition system (no points) like the later 251s.
The bike has been running fine in the past month that its been ridden since purchase. But now, after a short ride I stopped and a bit later it wouldn't start back up. Tried a few things, but ended up replacing the spark plug, after which it fired right up. Thinking it was the plug at fault, continued on riding for a few minutes, after which it just shut off and gave no signs of life when trying to start it again. I let it cool off for a few minutes and tried again. This time is started and ran fine and I was able to get it back home.
Currently (while its still warm), it starts fine, but randomly shuts off. When it dies, the charge indicator light as well as the neutral light turn off as well for a second, turning back on immediately after. I'm not certaint if this is related to the issue, but it seems like it either pulls to much power or looses contact for that brief second. Otherwise, doing a quick inspection, nothing stood out to me, no loose wires or connectors, the battery is good - sitting at 12.5V when off, and goes up to about 14.8V when the motor is running.
This is my first experinence with this particular ignition system so I'm not sure where the best place to start with is.

[DAVID THOMPSON]

clean the battery terminals and the spade connections to see if they have firm contact
most bikes after a few years seem to suffer from sick wiring harness
its been the most common problem with my rt125 and its a 2002

and its voltage regulator has had the spades removed and the wires soldered together
with shrink fit covers since it was about 2 months old the VR plug wires got stinking hot till
i soldered the hole mess in with out the spades
and my cars if owned by someone else would need an auto electrician on retainer
there is always some thing not working correct

[Puffs]

Removed

[Blurredman]

Which do you have, I wonder?







These three are all factory.
https://www.youtube.com/watch?v=vBiLutPTG-E


Unfortunately I don't have much to tell you about the factory contactless ignitions. But the ignition light actually turning off is a big/helpful sign.

Is it possible to ride around without the generator cover? When this stalling occurs, you able to get to a safe place and touch the sensor (red thing in this image, if you have this ignition, for example)? I imagine it shouldn't be too hot.. But it might be a bit warm from heat transference from the engine. Could also feel for the actual magic black box too. I know a particular varient of the original contactless ignition is not particularly reliable- sometimes they just go, and I'm unsure whether this is the ignition you have or the earlier one.

I would definitely check out the fuse box too.

My car about 7 years ago did this random cutting out, and then kicking back in- slowly it got worse and worse and worse, and would work fine cold for a little while, that turned out to be the ignition amplifier in the distributor... Now obviously my peugeot 205 is more complicated so the wiring isn't cost reduced so much compared to the MZ, but is it a possibility that the ignition is breaking down here? Do you have access to converting the bike to points?


Just a little looking around on the German MZ forum and I found this.

https://mz-forum.com/viewtopic.php?f=6&t=73333

https://1-mz--forum-com.translate.goog/viewtopic.php?f=6&t=73333&_x_tr_enc=1&_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp (english)


Sounds like same problem?

[Kruh]

Thank you, I will check and clean all the relevant terminals.


I have the ignition system like the one in your second photo.

Just a little looking around on the German MZ forum and I found this.

https://mz-forum.com/viewtopic.php?f=6&t=73333

https://1-mz--forum-com.translate.goog/ ... r_pto=wapp (english)

Sounds like same problem?

It does appear to be a similar issue. They are mentioning the ignition coil as a probable fault.
I did notice on mine, it was quite warm to the touch after that short ride. But, like I said, I'm not too farmiliar with this ignition system, so I have no way of knowing how warm they normally get. But, might be related.

[Blurredman]

Yes, it's possibly the coil too- but i'm not sure the ignition lights would necessarily turn off for a second and come back on?? However that is still a possibility, the symptoms are that of a coil failure sure.

I would clean up all connections possible, and carry on. Then swap the coil, then swap out the ignitition system I suppose.

[Puffs]

Removed

[Blurredman]

Did you get a resolution to this Kruh?

[Kruh]

I did. It turned out it was an issue with the carb, not the ignition. I did take the carb out a few times just too check, but everything seemed fine and clean every time it was off, and the bowl wasn't empty (though I didn't check exactly how much was in there).
And indeed, after trying to start it for a bit and replacing the spark plug it did run, which all led me down the path of blaming the ignition.
Only recently when I was testing things, I had a clear hose connected to the carb, I noticed the fuel level randomly dropping. Upon further investigation, there was a piece of something stuck in the carb inlet, which caused it to only occasionally let fuel through into the bowl, hence the odd behaviour of it randomly shutting off and not wanting to start.

[Blurredman]

Aha. Glad you fixed it


But curious how that influenced your dash lights?