Das MZ Forum für MZ Fahrer

First of all sorry for the english, have to use it since I don't know how write german.

I would like to know how the power reduction in the 251 ETZ is made? Mine is from 1990 and I have a feeling that it might be the less powerful one. Bought it from Vietnam in 1991 and it doesn't have oil-pump. But for some reason it has the rev.counter.
I'm a bit confused why they did two models of it?

The power reduction in the 251 ETZ is made by an longer Exhaust pipe.

The Exhaust pipe of an 21Hp-engine:



If you want you an order an 21HP-Pipe at http://www.mz-b.de/mz/angebot/english/eauspuff.htm
They made two versions of that engine because of some Insurance and license specials in several countries, the etz251 was exported to.

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Grüße

Christof

Organisator des ES-Schweinetreffens in Coppanz 2013 & in Bucha 2015

Rundlampenschweinchenliebhaber Nummer 082

Kämpfer für das Überleben des 175er Ersatzmotors 4539110

Hi Teemu,


It ist not only made by the Exhaust pipe !There is some modification in the Carburator to.
The 17 HP Version Carburator has nozzles ( at least the main nozzle!) with smaler diameters.
Please have a look into a Spare parts catalogue or contact a Dealer like GUESI
( i´m shure he speaks english ).
Or better, I believe you are looking for more power, write us what kind of Carburator you are using,
how ist the marking at the main nozzle. Is there are a "13KW " marking, with an additional marking of the old MZ Sign, close to the Cylinder at the exhaust pipe ?
The 21 HP Exhaust pipe have to end about 4 centimeter in the Muffler, without any markings everywhere.

@Teemu, where are you from? Because you wrote that you bought your MZ in Vietnam ?

kind regards

Norbert

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Gruß

Norbert

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separatistischer-Inkognito-OT-Partisan

Thanks for the quick answers.
My carburator is the standard BVF. Unfortunately I don't have it at home so I can't check the nozzles right now but I'll look them as soon as possible. Maybe I should change it to a BING?
I have a new muffler in the bike as the original one broke. The forward exhaust pipe goes into the muffler only so that the seal is tight.
If it would be cheaper I'd take the bike to a dyno to know for sure
I'm from Finland but kived in Hanoi for a couple of years in early 90's. Tax-free bike. Some bring BMW's and other expencive bikes, I brought the MZ. It had about 7000 km by the time we bought it and it costed 500 $ at that time. Now I have the engine out of the frame as I have repair the clutch and had it bored (?) to second oversize at once. I have ridden about 100k kms with it, strong bike.
Next big overhaul will be the modification to 300cc. Perhaps next winter.

Terve Teemu !

Hauska tavata. Olit ilmeisesti Multialla kokoontumisessa n.15 vuotta sitten? Sama paikka jälleen 12.-14.6.Koetahan tulla!

Timo,(Multia)

Moi
Siellä olin ja tarkoitus olis tulla taas jos vaan saan koneen nippuun. Jääny ajot vähiin viime vuosina saamattomuuden ja kytkin ym ongelmien takia. Mutta yritän kyllä tulla sinne.

Main nozzle of the BVF in my bike is 130. Standard I think?
The only real problem with my bike has been clutch drag right from the beginning. I have never got it working totally perfect and last time I rode the bike it started slipping. Now I have the clutch dismantled and the plates are "glassed" ie. shiny. I sould maybe change the friction plates. How about the springs? And does an ES clutch fit hte ETZ?

es wäre schön, wenn ihr uns an euren Erkenntnissen teilhaben lassen würdet, englisch ist ja, wenn es sein muß ok, aber ich habe gelernt, die Forumssprache ist deutsch!

Sorry for the finnish in between.
I do not know what you wrote so.... I write in english because not everyone in this world knows german, sorry. Even though I ride an MZ. And if german was the only language in the forum I'm sorry, this will be my last post then.
Thanks for the help anyway.

Hey Teemu,

don´t bother about some newbies in between our community...who speak neither finnish nor english...
You are of cause very welcome here, some of these guys just ...hmmm, just forget that comment in german...
(By the way: it just meant: " please, if you found out something, let us participate...")

Regarding your clutch drag: Glassed friction pads?
Sounds like weak/wrong/too short springs to me or just worn pads.

Do you have a repair manual for the MZ - I guess you have, but nevertheless:
the spring length (expanded) should be 28,3mm (+ - 0,6mm),
when installed the compressed length should be 17 mm, with an elastic force of 130N.

To check the wear of the clutch friction pads you have two possibilities:
Short one: there is a gap between pressure plate (the one moving which is pressing directly on the friction pads) and clutch outer ring - this should be more than 0,5 to 1mm otherwise the clutch is worn.
The perfect one: Measure the friction pad thickness - New is 3,0 + - 0,1 mm, worn is 2,7mm.

By the way: you said it started slipping quite abruptly - did you change the oil before that?
If you did maybe the oil was the wrong one - always use an oil with low additives - e.g. GL3 qualification.
(Standard comment, don´t bother, please.)

You can fit an ES clutch which is basically the same - except for the ones with an axial bearing, I believe the clutch lever (pusher) is a bit different.
But if you have a spare clutch with good parts - you can mix the main parts if everything else fails...

So, have fun with your bike and
Best regards to Finland!

Jan

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Suche dringend: Mehr Freizeit
Platz habe ich ja jetzt wieder ein wenig...gehabt...
Ach ja: einen Fortschritt hab ich jetzt auch...

Sorry for everyone, Monday mornings are not always easy....
The finnish reply concerned only the participation to the 17th Int. MZ-rally in Finland, nothing else. So no help from there.

I'm trying to get new friction plates from a local supplier, also the springs. I will not put the old ones back as I finally got the clutch disassembled. (not an easy job as it has been in place for 18 years or something )
I measured the plates and springs and they seem to be inside the changing tolerances. I really do not know what caused the problem but it has been there for whole the time I have owned the bike. I have tried to adjust the cable and done everything that was possible without dismantling the clutch but nothing helped. I guess the slipping started because I did not change the oils. Drove with quite old ones and also quite brown when I drained it. For some reason I get water into the gearbox.
Now when I will assemble the engine again I'll put some silicone or sikaflex to the clutch cable end. Also I think that the oil inlet (rubber) lets water into the gearbox, I must propably put a plastic hose to it.
I got the ES (I'm not sure even about that) clutch for lend and the body of it is almost 10mm shorter than my clutch, that is the reason I asked. Don't think I'll put that into the machine.

And thanks, I have had fun with my bike and hope that I'll have fun in the future as well!

And if anyone knows a better translation machine in the internet than babelfish please let me know. It would be nice to look into this forum more deeply.


p.s. does anyone know the lenght of those exhaustpipes? The difference between 17ps and 21 ps in mm's?

Hey Teemu,

the water in the oil is prevented best by one of these rubber plugs which shield the point where the cable enters the sleeve (already installed on new clutch cables), but I think sikaflex will do it as good.
The rubber plug for the oil inlet is not a problem - usually.

Did you try the rough clutch adjustment under the tachometer drive cap on lefthand engine side before adjusting the cable at the handle?

There is an MZ-rallye in Finland? Great!
Where and when?
Some Friends of mine are already looking for a good reason to travel to Finland again!

Have fun!

Jan

_________________
Suche dringend: Mehr Freizeit
Platz habe ich ja jetzt wieder ein wenig...gehabt...
Ach ja: einen Fortschritt hab ich jetzt auch...

Hello Jan,
Ihad the rubber plug in the old cable and also in the new one I just bought but I still think I'll put some sika to it, just to sure no water goes in through the cable housing. Also the rubber plug and the hose to it is only as an extra prevention, I don't think water could enter through there.
I tried the rough adjustment too. Also I consulted some local "gurus" to help me without success. Thats the reason I have the clutch in pieces now waiting for new parts. I'am not quite sure how the bike was transported to Vietnam and what kind of, if any, service they did to it. Also might be that they used some wrong kind of oil in the beginning and it ruined the clutch.

The MZ-rallye is 12.-14.6. http://personal.inet.fi/kerho/mzajajat/english.htm

Welcome to Finland! I really hope to get my bike in one piece before that.

Teemu


edit. I put some pics of the bike and one of the clutch plates on the pic folder.

I wouldn´t do that as long as the BVF still works!
If you use English here, it´s o. k.!
You can also find manuals in English here: www.miraculis.de
Greetings to Finland!
Martin.

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Liste der großen TS

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