MZ/MuZ Riders

Hi, my Mz etz 251 has been laid up for a long time
And now wont start, they seems to be no spark and the coil is getting hot
The bike ran fine a while ago.
Can anyone help.
Thanks dave.

Seems to be no spark? there is either no spark or spark, surely?

Electronic ignition or contact breakers?

If your coil is getting hot it's constantly being charged, because for instance your points are corroded shut. Or something else is wrong. I think the advice is to check your ignition.

On the up side: the battery seems to work.

Hi,took engine case of and the electronic ignition
was very corroded.
I cleaned it up best I could but no joy
Can these be repaired or can you still buy new ones.
Thanks dave.

Hi Dave,

pics would help.

Yes, you can buy anything for these bikes, see for instance viewtopic.php?f=5&t=9257

Hi, cannot get picture to load?
Does anyone know how to remove all of the electronic ignition.
I wanted to see it had corrosion behind it.
Thanks Dave.

Sounds like the electronic box or sensor is fried if the coil is getitng hot as it is continuously passing current.

Could understand if it was points stuck closed.

I had an ETZ 301 and that had electronic ignition - the sennsor was easy enough to remove as if memory serves it was obvious which screws held the sensor in.

Good luck.

Just an update, put plug in and it did not spark but when put back in bike I kicked
The engine over a few times and nothing happened
But when I turned the ignition of it backfired
And a oily mixture splatted on back of my house.
Does anyone know what could be wrong
Thanks.

Take the spark plug out

Then turn the ignition on. if it sparks when the ignition is turned on, I think the black box is blown, likewise when turning the ignition off.

I have done this myself by mis-wiring the system before now.

I think your electronic ignition is constantly passing current through the ignition coil, which is why it gets hot. It is like a conventional breaker points system, where the points constantly make contact with each other, and do not open when they should to make a spark. Normally they're open for about half the cycle, so that the coil gets charged only for half the time, and I guess with an electronic ignition it should be similar.

To answer your question, I think the following happened: apparently corrosion has got the better of your ignition, and it continues to make that contact. When you switched the ignition off, that contact caused a current fluctuation, apparently enough to cause a high voltage in the ignition coil. That in turn caused a spark in the plug, thus igniting the fuel that remained in the barrel. Apparently the piston was in a lower position (or pushed there because of the explosion), and after passing through the exhaust port, the hot gasses caused the oily fuel mix in the exhaust to also ignite.

Please do the test Blurredman suggests, and you can see the spark for yourself, occurring when switching the ignition on/off (& v/v). You're then using the ignition switch as breaker points.

It should not be difficult to get the old stuff off, but I don't know your system & without pics it will be difficult to advise. Uploading pics should not be difficult either.

For instance, if you select the 'Upload attachment' tab right below where you are typing a reply to this post, and press the 'Browse' button, select the pic you want to upload. Then select 'Add the file'.

You can then select 'Place inline', or not.

Pic of mz electrics.

From which ocean did you pick that out of?

Nah I joke- but seriously- I had the same ignition that I blew- Did you try as I suggested?

Ah, the miracles of archaeology.

Ta for the pic.

A gentle blow with a small hammer on the end of the Allen key should release that hex nut, so that you can take off the trigger unit. The current breaker part of the ignition comes of with the adjustment nut at 11 o'clock. But you may want to dismantle the generator to clean & inspect it. Look in a manual, see Blurredman's signature. With the ignition removed, take off the brush unit, and then the stator housing with the 3 screws at 120°; that's probably enough for cleaning. You may want to do some tests with a multimeter too, to check the generator.

Most likely, the generator will only require cleaning (maybe some new brushes), but you will need to replace the current breaker part of the ignition, assuming it fails said test. There are several systems you can buy for that engine.

Good luck!

Hi,thanks for all your help.
I did remove the generator cover and cleaned it out, it was a bit rusty, I think I need to strip the generator and get any corrosion of the parts.
I have some new brushes and the part the brushes fit into(sorry don't know the name)
I don't know were to connect a mutil tester to test things as I cannot find my Haynes manual!