Das MZ Forum für MZ Fahrer

Hi guys and gals, I have a problem I need sorting out, maybe the knowledgeable members could assist me.
I have an MZ ETZ 250 first model that will not start after an electrical short circuit long time ago. I repaired the electrical system as much as I could - changed burned out cables and installed new battery. With the ignition key I can cycle trough the different modes to start the bike and the lights on the speedometer will come one, but there is no spark at all.
I understand only mechanics, electrics are not my strong side. I see there is bunch of cables and relays and resistors and stuff under the seat, but I really don't understand them all.
I want to ask you: is there a simple way of connecting just the necessary components to make the bike start? Like maybe high voltage coil to battery and to spark plug and to voltage regulator or similar. I am really not knowledge in electrics, so maybe someone could draw a map of only necessary connections of components to get the bike started? So basically only the absolute minimum connections to get the engine running, no lights, flasher and such.

I also checked online for electric chart/drawing for the MZ ETZ 250, buy only found black and white drawings or color but for the Etz 251.
Around where I live there are no specialists left that could fix old bikes like the MZ, so I have to fix this problem myself.
I got new coil, spark cable, spark plug and battery. what should I do to get my bike started, any suggestions?

Thanks,
George

Hello George,
our net-harry memberlist.php?mode=viewprofile&u=1808 has a coloured one in his signature:
https://pic.mz-forum.com/harry/MZ/Schal ... etz250.pdf
Hope it helps a little bit!

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Perhaps this will help: Minimal ignition circuit https://pic.mz-forum.com/lothar/Elektri ... age055.gif

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Grüße

Frank

yes, the image linked by Frank would be the least connections you need to run the engine.

For translation:

the rectangle top right is the coil; the inlets should on the coil show the numbers given in the image. The arrow pointing left is the cable to the spark plug. Batterie is easy to translate and should be obvious .
Bottom right is Unterbrecherkontakt = Breaker contact and Zündkondensator = Ignition condenser. Both are found on the right side of the motor under the lid. Make connections between them using rugged cables.

Good luck!

wow guys, you are such a great community, hats down for that
I will try the simple diagram and post results.

Is the bolt shown on the bottom next to the spark plug a ground? It's hard to tell

edit: oh that is the small capacitor right.

I will try this tomorrow, hopefully will find out if the engine is ok. It turns and changes gear freely, so I hope just the electrical system needs to be refurbished.

I want to keep this bike original, but if I have to do engine and trans work I might restore everything to new, we will see.

I will keep you posted.
thanks again

Hi,
on the pic, the Spark Plug is not shown !
( It is the black Kable with the Arrow in the left upper Corner.)

Bottom middle is the Capacitor with his Screw.
Bottom right ist this: https://www.google.de/search?q=unterbre ... 24&bih=947

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Mitglied Nr. 066 im Rundlampenschweinchenliebhaberclub

Lothars Fibel für Vergasereinstellung: http://pic.mz-forum.com/lothar/SONSTIGE ... ungBVF.htm

ES 250 Kickstarterantrieb auf jeden Fall auf TS oder ETZ wechseln !
siehe: viewtopic.php?f=4&t=30624&p=1158985&hilit=kickstarterwelle+ertz#p1128457

lol, yes I made mistake above, you are right, the spark plug cable is between (1) and (15) terminals on the coil. I was wondering I don't see how to make the actual connection on the braker, but probably once I open the engine cover it will be obvious.

by the way, how do I do it? do I just connect the power (+) wire to the battery and try to crank? and once it starts do I disconnect the battery? probably not

Yes, it is only for short testing, not for use on Street !

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Mitglied Nr. 066 im Rundlampenschweinchenliebhaberclub

Lothars Fibel für Vergasereinstellung: http://pic.mz-forum.com/lothar/SONSTIGE ... ungBVF.htm

ES 250 Kickstarterantrieb auf jeden Fall auf TS oder ETZ wechseln !
siehe: viewtopic.php?f=4&t=30624&p=1158985&hilit=kickstarterwelle+ertz#p1128457

You can also do the following measurements with the standard cabling:

* remove the alternator cover on the right side of the motor (you probably already have this removed)
* check that the breaker contacts are open, if they are closed slightly turn the crankshaft until they are open
* turn on ignition
* check if point 15 at the ignition coil has > 12V, if not => why? Fuse? Ingition switch? Cables? Battery charge? Fix it.
* check if point 1 at the ignition coil also has > 12V, if not => either the ignition coil has an interruption and is broken, or something is shorting pin 1 to ground (broken capacitor, breaker that makes contact even if the contacts seem open?)
* check if the breaker's side of point 1 also has the same voltage as on the ignition coil (cable broken?)
* turn the crankshaft until the breaker's contacts close. Now you need to measure close to 0 Volts on point "1" on the ignition coil
* if you now open the contacts, the spark plug should spark

Note that you must not keep the ignition turned on with the breaker's contacts closed for a longer time because this might damage the ignition coil (it will overheat).

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Gruß, Stefan

so, I tried the simple hook up and unfortunately no luck. there is not even a try to start, totally limp.
I changed the small condenser, but no luck again.
The coil is new, the spark plug is new, the sparkplug cable is new, condenser is new.

Any suggestions what should I do from here on?

I was thinking maybe the alignment on the breaker is off, but shouldn't it try to start anyways, even with bad alignment?

-- Hinzugefügt: 18. December 2019 12:48 --

just moved the bike to the basement. put another spark plug in the cable, grounded to the cylinder head and cranked... no spark.
So probably the cable to the spark plug is not good or the brand new coil, am I missing something?

What is you opinion?

also the braker opens, I can see it while hand cranking the engine.

did you adjust the breaker contacts correctly (0,4mm distance)? do this first, before changing other things.

I bought a new braker and new eccentric cog and will try to install then tomorrow.

In remember the braker was tough to align - have to remove the sparkplug, and for the cog I am not even sure.
Thank you for the suggestion, I will replace these two parts tomorrow and will also measure voltage at the coil and braker per the post above.

I am sure you have on the forum the instructions for braker alignment, could someone share the link to the tread? I use Google translate for the pages in German, so should be able to figure it out.

Where is your alternator-/ engine-ground ?
-> Where does the brown wire end that comes with all the other wires from top-left ? It should be connected to the tab at the capacitor mounting bolt.

lowest-level-check:

1) put the spark in it's connector, rest it on the cylinder with somehow-contact between cylinder surface and sparkplug shield/thread. (ground connection for high voltage)
2) ensure breaker is opened (rotate crankshaft as required)
3) turn on electricity, maybe re-check: 12V is present at [(15) ignition coil] and the "center contact" of capacitor
4) use a screwdriver to short-circuit the breaker. (coil gets charged) ..fractions of a second are good enough
5) when you release/open the the breaker a spark MUST be generated and visible. If your coil and the sparkplug,connector+cable are ok.

U can "fiddle" the breaker with the screwdriver to generate multiple sparcs...easier to watch.

or:
Instead of using a screwdriver you can also use the green wire from capacitor to ignition coil: unplug it from capacitor, grab it's end and tip-touch the housing-> same effect
BUT CAREFUL
The primary voltage of the ignition coil (a few 100V) will apprear at that end of the green wire. Not dangerous, but inconvinient. so better wear leather gloves or grab the wire with isolated pliers.....or use the screwdriver method.

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Für den Erhalt der elektromechanischen Corned-Beef-Dosen-Regler !

thanks, I will test tomorrow and report the results

-- Hinzugefügt: 19. December 2019 11:19 --

so I tried what Torbiaz suggested:

with open or closed braker I get 12v on coil (1) and (15) contacts in both situations (open and closed). If I jam the screwdriver I get short and also a spark from the sparkplug, also get momentarily a drop in coil (1) to 0.5v. is this the way it should work?
If this is the way it should be, but I cannot get the engine started does it mean I need to adjust the braker? is this the problem then with my no start?

-- Hinzugefügt: 19. December 2019 11:26 --

so I cannot repeat the process as Torbiaz suggested: I do not get the spark when I open the braker. I get the spark when I short the braker with screwdriver. I spin the engine with a wrench and there is no spark when the braker opens and closes. I get spark only when I short the braker contact with the screwdriver.

The spark is generated when the breaker opens the contact (or or the shorting srewdriver is removed)

This happens rather "accidently" because you actually cannot really hold the circuit closed/shortened.
So this looks ok to me.

Also the drop to 0.5 while shorting is correct.
The breaker/srewdriver connects the coil to ground which closes the circuit and current flows through the coil.

so the last suspect is the breaker.

...indicates the breaker is not working properly.
Brushing and cleaning the contact section (removing erosion) and re-mobilising the joint might bring you further..... or you have to get a new one.
When re-assembling take care: that little piece of felt is not allowed to be between the contacts or the lever and the cam.

Re-install the breaker and adjust the maximum gap (where the breaker opens widest while turning the crankshaft) to 0.4mm.
-> excentric Bolt near the lever joint

Set Timing: Breaker has to start to open at 2.5mm before top dead centre. You can monitor the voltage drop from 12 to 0 to find the correct moment.
-> oblong holes on the very left.

should work.

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Für den Erhalt der elektromechanischen Corned-Beef-Dosen-Regler !

Torbiaz, you are correct, just changed the braker and now when I spin the engine I get a nice fat spark, Soo happy. I looked at the old braker and it seems the contacts have some bi-metal plates, that we're worn down. now this is fine, I just need to figure out how to the the braker alignment.

I want to change the cam shaft, do you know by any chance how to change it? I bought a new one as well, you can see the part in the first picture.

The second picture is of a plug that is leaking oil, any ideas how to fix that?

-- Hinzugefügt: 19. December 2019 17:25 --

the plug is the little circular piece next to the sensor. it seems it was pushed in and now it is sitting tilted, so it is leaking

you:

me:





remove the bolt and remove the cam. there's nothing more to it.


The Neutral Gear indicator switch.... you have to remove it (oil comes out - so drain before), clean the thread, seal and remount it.
And if it's badly broken you'll need a new one.

edit:

No, I was wrong, you talk about the piece of metal left to the switch..... let the motor experts tell...

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Für den Erhalt der elektromechanischen Corned-Beef-Dosen-Regler !

clean the area with brake cleaner and cover the plug with some cold steel, jb weld.. you don´t need to open the plug anymore.

ets-g I was also thinking to use cold weld/epoxy resin, but was hoping there is a way to fix this plug so it looks factory. I can see it is tilted and not seated property in the hole, how did that happen I don't know. I don't even know what the purpose for this plug is.

I followed Torbiaz instructions and set the TDC back 2.5mm and tried to get the motor started. no luck again. I have spark but no ignition. I removed the air filter and sprayed gas mix with 2t oil in the cylinder and fired right up. The carburetor is leaking from the bottom like crazy, but the fuel doesn't get to the cylinder.
I rebuild the carb last summer, so don't have a clue why wouldn't it work.

-- Hinzugefügt: 20. December 2019 12:10 --

maybe from 6 months of seating the card is blocked again. I will have to dissasembly ,clean and try again.

For right now at least I know the ignition is working good and the motor runs.

I made this tool from a spark plug to measure TDC. I used 7mm bolt for the plunger... I am sure you guys know this way to make the tool.

-- Hinzugefügt: 20. December 2019 18:01 --

I was thinking maybe best is to buy new card. here I can get Chinese and Taiwanese make copies. I think Taiwanese should be better quality, has anyone tried these?

China
30N2-5
30N3

Taiwan
30N2-5
30N3-1

Mine is 30N2-5, is one of the other versions better in anyway? Seems 30N3-1 is the latest design, so is it better than mine? should I get 30N3-1?

thanks for all the help

This is a known issue for the 250ccm engines.
Your plug is done by factory from my point of view. This is only a sealing for the drilled hole in the gearbox compartment. Behind it is controller axle(see picture of my MM250/4 which has the same gear as your EM250).
If this axle can move a little bit sideways it can move this plug too.Perhaps this happened here. You can use hammer and punch to correct the tilted position of the plug.
When I overhoaled my MM250/4 engine I also used preventive epoxy resin to seal all the little metal plugs because this leaking is an known issue. But at this plug also cracked the resign when in use. So I used a more elastical sealing paste DirkoHT which is also used as engine sealing. Now this works fine forthousands of km.
If you want the factory look you can only use a new plug bring it in position and hope.
The only not factory looking thing at your plug is the 2 punch marks. Perhaps somebody also wanted to fix this drifting of the plug in the past.

According to your spark:

This is known but I think the most people here use an indicating calliper like this https://www.ostoase.de/Zuendeinstelluhr-Messuhr-fuer-Simson-Modelle. This is a little bit more precise. For a first test your method will also work.

I haven't yet understood whats wrong with your original carb. Can you explain? The better whay instead of buying this shitty chinese carbs would be overhoal the original one.
The 30N3-1 version should be the latest version but I'm not 100 percent shure but I think the 30N2-5 should be the correct one for your ETZ. Perhaps the more ETZ specialist guys can correct me if I'm wrong.
Nevertheless both should work with your engine if correctly adjusted.

Another option would be a BING carb which I also use(see signature). https://www.guesi-motorradteile.de/index.php/deu/704/_/c/Vergaser_BING_84_30_110A/_/?_This is the carb used in ETZ exported to West Germany as far as I know.
As I understood you live in US. So I don't know if you can get this one. Some of our dealers would also sent it to US but perhaps taxes can make this unattractive. The good point is that this you one can buy as new and it is even better than the asian replicas of the BVF. This is indicated by the feedback of some users here in different carb topics.

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zweitaktende Grüße
Chris

TS250/1 BJ 1979 (die Biene)
Yamaha XS750E BJ1979 (der Elefant)

Thank you OChris, I folowed your suggestion and used small hammer and chisel to put back in place the little drain plug. seems it is not leaking now, but will know in couple of day for sure. if it leaks I will put cold weld, probably will look better than the gasket maker silicon. If this fails I will put silicon in the end:)

Yes I know Chinese carbs are trash, I would like to get German made card, but here they are hard to get by. I was thinking to get carb made in Taiwan, probably better quality than Chinese. I an not sure what are the differences between 30N3-1 and 30N2-5 which is original model for me. that is why I was asking if the later model is better or not, if someone knows let me know.

As for my own carb- I cleaned it and put new Jets and gasket and everything, but it doesn't work. It doesn't let any fuel go to the cylinder. The carb leaks from the bottom drain, so I guess the float is not adjusted as well. There must be some internal blockage and the fuel doesn't get to the engine. Is there a way to test the carb and find why and where it is blocked?

I read a little bit in "Wie helfe ich mir selbst" Heinz Neuber, Karlheinz Müller 3rd edition 1988. This is a how I helb myself book for MZ.
They say since 1987 the ETZ 250 and 251 have used the 30N3-1. Before that the 30N2-5 was used.
A main difference is that the 3-1 don't use a screw on the damper slide for idling system. It uses a special air circulation system for that purpose- that had something to do with exaust regulations at that time. There is a special air screw for adjusting idling like in more modern carbs. For environmental reasons this screw is fixed in factory and plumbed.



Sounds like a bad fuel level or adamaged or polluted float needle valve. You can have a look on http://miraculis.de/aw/mz/mz.html there is one english version of the smaller etz150 repair book from Zschopau. Select "Bücher" on the left and go down to ETZ! The carbs should be nearly the same like in the ETZ250 but smaller than that. Somewere should also be an english one of the ETZ250 in the www but I don't know where. The level of the fuel is different but the adjustment should be the same.
You have to find a glas to put the upper carb like in fig181 into it. Connect a fuel tank and look for the level. If its wrong use the explained way to correct to 14mm +-1mm.

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zweitaktende Grüße
Chris

TS250/1 BJ 1979 (die Biene)
Yamaha XS750E BJ1979 (der Elefant)

I found a body from original carburetor 30n2-5 for 43 Euro and bought it. Will fit all the Jets and test. Will post what will happen

Hi and Happy New Year.

I got my carb rebuild with new NOS main body, new float and needle and Jets. I want to ask you what are the basic settings to get the carburetor adjusted so I can mount it on the bike and start fine tunning?
I have seen pictures of the carburetor for the MZ 150 with some lines to get the float adjusted, can you tell me what are the measurements for the MZ 250 carb? Please have a look at the picture I made and help me out with some guidance.

Also I tightened the adjustment screws all the way down. Do you know how many turns I need to turn them? I read somewhere that it is 4 turns, but I am not sure this is correct.

And finally: I need to replace the main needle, it got bend, but now I am not sure how to attach it correctly and at what level. There are four levels, which one is default?

Thank you guys

Hi Turbinee,

all what you need you will find here: http://www.miraculis.de/aw/mz/mz.html
"Bild 195" (around picture 195")
With the needle I woud start one position higher (3rd position)
The right screw is for air in "Standgas" - the manual says for the carburetor BVF 30 N 2-5 only one turn open (section "1.2. Vergaser")
More importend is to start with a nearly open (left screw) for running idle "Standgas2, than you have no "Standgass" but it is not neccessary for 1st start. If the screw is too much in, then the running idle "standgas" is to high and the engine will overrun.

The good tuning procedure is descripted here, maybe google translator will help
https://pic.mz-forum.com/lothar/SONSTIG ... ungBVF.htm

I hope it will help, please contact me if you need more help in translation e.g.

Regards

Dieter

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Was ich an MZ wirklich mag: 1x fahren = 1 x schrauben - dafür bei mir komplett ohne Elektronik