Das MZ Forum für MZ Fahrer

Hello!
I have to consider a total renewal of my ETZ 251 engine during the winter as I lost the third gear and the engine sounds as there are few bearings broke. How big operation is it to take the engine into parts totally? Do I need any special tools or is it possible to do with normal tools? As for now I have only renewed the clutch so it requires somewhat more work. I really hope to be able to do it during the winter.
I could buy a "new" engine but then the problem would be the local "TUV" here which is expencive and anyways I want to repair the original engine.
I assume that new parts for the engine can be bought at least from Germany if I am not able to find them locally.
Thanks already.
Teemu

Soweit reicht mein Englisch nicht.

Du brauchst den Abzieher für die Kupplung für ca. 30 Euro. Niemals mit einem anderen Abzieher probieren!

Gut

http://www.ost2rad.de/shop/cache/867473 ... f3f31d.jpg
Bei http://www.ost2rad.de/shop/ Art-Nr. 1961

Schlecht

http://upload.wikimedia.org/wikipedia/c ... rekker.jpg

Alles andere geht mit viel Wärme.

Zum 3. Gang:
Die Zahnräder Schaltrad 1./3. Gang und Losrad 3. Gang und die Schaltgabel müssen getauscht werden. Achtung: Die Zahnräder sind nadelgelagert!

Do you have a repairing manual?
If it is your first MZ engine to repair you need a manual for sure.

You need a special tool: You have to pull the clutch from the crankshaft .
Dont buy the cheap clutch remover !!!

Edith talks with babelfish and says the special tool is called Clutch puller

Disassembly + assembly only wenn the engine has a temperature of at least 100 degrees centigrade.

As a beginner it will takes about 1 day for disassembling, cleaning and separating all the engine parts.

Assembling, if you have all the Parts you need, will take about another day.

Look for the repairing manual and then better look for somebody who had done this job before.

It ist helpfully, if you can buy an old or ruined 5 Gear 250 cc engine from MZ ( TS 250/1 up to Kanuni ETZ 251/301 )
for training disassembliing and assembling ( you can do it with old parts. )

Hello,
I have the Haynes manual and also a copy of the original manual for the 250 in German so it might help me a bit.
Do you mean that I have to warm up the whole engine when taking it to two parts? I thought that the only place is some bearing that needs heat to come out.
I have a clutch puller, though its a cheap one similar to the original. It might be that I destroyed the crankshaft when taking the clutch off last spring.. Too much force I think.
So I have to be careful next winter.
I have to post some questions here when I get the engine apart as I probably need help anyway. For now I have to ride with four gears as long as the weather permits, it is quite difficult to drive on small roads as the third gear is missing but I do not want to take it to the garage yet.
Teemu

Da gabs doch mal englischsprachige Filme bei Youtube von MZ direkt wo gezeigt wird wien MZ Motor zerlegt wird. Kennt noch einer den Link?
-Dem Mann soll geholfen werden!

-- Hinzugefügt: 13.09.2009 20:45:58 --

I Found it!!!!!
Start "youtube.de" and search for "MZ Maintance" there you found what you are searching for. Of course you need some special tools.

IMHO is it only Assembling, and you can make some Mistakes while disassembling....

-- Hinzugefügt: 13.09.2009 21:57:27 --



Disassemble every Part you can on the right and left side of the engine (including clutch). Pull off Cylinder. Disassemble the Piston.
Than heat up the rest for about one and a half hour. If you have not forgotten a single screw the both parts of the engine should separate with very little power.
Send a picture of your clutch puller. You need the little Adapter ( DRUCKSTÜCK ) very urgent !

It is very often not the maximum of Torque that pulls the clutch from the crankshaft!
Use a Hammer and hammer it on the clutch pullers screw ( not the Big Bang! - it is hard to describe in english how to hammer).

Better look for some help by an experienced MZ Driver.

Some pictures concerning engine dissambling
Unfortunatly, only from the body of engine without attached parts as clutch and so on

Teemu, are you experienced in the function of the gear box?
As Lorchen tried to explain, the gearwheels have catches which have abrasion.
These gearwheels have to be changed, some further parts may/will have been changed too.

Sorry for my poor English knowledge, but if appreciated, i'll try to give further information

Hello,
I have never disassembled the whole engine before. Every bit of information is very welcome, even in poor English or good German.
So the gearwheels marked with an X in the photo above must be changed?
The clutch puller that I have is similar to this one: clutch puller
And I made a big bang on the bolt as the clutch was very tight.
I am really thankful for all the help I have got here as it is then more easy to go on with the job. Maybe in a month or so I'll start the work.
Teemu

Nein. Das X markiert den Eingriff der Schaltgabeln.

From what I've seen on Youtube there are Videos from Assembling AND Disassembling that you can Download

Ok. Is it possible that one of the Schaltgabeln (?) is broken? Or which part changes the gears?

Nein, die Schaltgabel ist nicht gebrochen. Sie sieht aber so aus.

Looks bad. You have experience?
I can not wait to see mine...

Total renewing of the engine is a must now as the engine finally broke down. Seized at approx 100km/h. Not so nice. Probably bearings in the gearbox broke which led to the seizure. Compression is totally lost. Piston still moving but no compression.
Now I have to see what is broken and decide weather to fix it or buy something else, depends how much is broken.

I'll post pictures as soon as I get the engine open.

Hello Teemu,

I wrote a short abstract about diagnosis of problems dealing with the gear box.
Please send me a private message with your E-Mail address, so I can send you this abstract.

Are you absolutely sure about the seizure?

By removing cylinder and piston you should get enough information whether the crankshaft is involved.
As you mentioned a loss of compression, I assume some piston rings broke.
Some informations of demounting and mounting of cylinder and piston you should get from the repair manual of ETZ 150 (concerning the cylinder it is similar to ETZ 250), which can be found here
http://www.infomate.de/miraculis/aw/mz/ ... z15re.html
For being written in English, this may be a better help for you than a German description...
The gudgeon pin can be removed by hand when the piston is heated.

Furthermore, broken shaft seal rings may be a reason for the loss of compression.
After dismantling these seal rings you can have a look at the bearings of the crankshaft.
Clutch and dynamo have to be removed.

But first I'd suggest dismantling cylinder and piston and taking some pictures for us

did you read your PM box? sent you mail.

This Clutch puller ist not a good one !

Hello again,

Long time and no significant moves on my bike. I took the exhaust off and took a photo into the piston, does not look good. More when I get the engine off the chassis.
So it was not the gearbox but simply old fashioned piston ring breakage.

Hello Teemu,

it will not be neccessary to take the hole engine out. Untighten the screews for the upper holder of the engine(thatone on the head of the cylinder), open the chain or untighten the chain tensioner and release the engine as far as possible. Now you can disassemble the head and the cylinder. If you want to go on with the idea to repair the hole engine and gearbox, you have to take out the engine

Hello Teemu
============

Your piston is done, but mostly only a new Oversize-Piston is needed. Please remove the cylinder and the check the crankshaft for several damages. Maybee this will help you:

http://www.dgw.org.uk/downloads/mz-etz- ... 81-ocr.pdf

Hi Teemu,

I have very little used 251 cylinder for sell if you are in need to replace it. Furthermore, I could drop it to a post office in Helsinki.

Argo

Hello.
A small step forward on repairing the engine.
This is the reason that leaded to breakdown top end bearing. Looks like the service limit has been exeded.
Rest of the bearing is somewhere down the engine....
Is there any way to break the engine in half other than the mz-tool?

Hey Teemu,
ouch, that bearing has passed away to Nirvana...
If the shattered remnants of the bearing are somewhere in the crankcase - you could try flushing it out and puzzling the pieces together to see if you have all parts...
(But for my part, I would perhaps split the engine, too.)

Opening the engine is easiest with the tool or a similar device, in my case a large U-shaped steel bar, same length as the engine, does a good job. I welded three latches to it to bolt it to the right half of the case and tapped two M12 threads in.
Apply enough heat and the case will nearly fall apart without use of tools.
(Some say that two large screwdrivers, carefully used as levers in between the sealing surface are enough tooling for a quick split of the case halves - but that´s quite risky and just an emergency solution.)
Regards
Jan

Hi Teemu,
pic 24+25: the ball shall not remain in the bolt, there is a spring behind. Wrong ball diameter? (I guess it is 8 mm).

Seems the engine bloc is ready for disassembly. Clean it with a high pressure washer, try to remove as much oil and dirt as possible.
Then wait til you're alone at home ant put it in the kitchen stove, 150° for one hour. It may smoke! Smells disgusting! Sticks to the flat for days.
Cover the kitchen table with a good layer of old newspapers. Now two persons are the best: one holding the bloc, one tapping gently with a rubber hammer on the shafts. But you can do alone as well.
There are two bushes that may not separate easily, one in the M8 front bolting, one in the upper rear bolting. Wooden wedges are better than screwdrivers to put them in-between the halves of the bloc. Do not hit on the cooling fins, they break.
Once the halves open, you can pull everything out gently. And see what you've got
Greets
Carsten

Hello,
I heated up the engine by to hot air guns and got it into two pieces.
This might be the reason for losing third gear. There are signs of wear on the shaft. Otherwise the sprockets seem to be be in reasonably good condition.
Pieces of the broken bearing had got their way to crankshaft bearings, evidence. Also they made a nice scratch to the engine half.
Some freeplay on this part comparing to the other side.
Cylinder head is maybe beyond repair?
This is something that wonders me, why is the ball stuck on the bolt? i have never taken it off before, so if the ball is wrong size it must have been put there in Germany. The ball goes in to the bolt and the spring is somewhere under but I can't get the ball out. Does it matter if it is inside?
Now I have to think which parts have to be renewed and then think if it is worth it.
After all I've seen new engines for sale. They just cost a bit too much.

Hi Teemu!
So far- so good. Maybe not. The shift fork is only the result of the damaged gearwheel claws. I saw some of them rounded. If the surfaces are not straight and under a small angle, that keeps the wheels together under load, they tend to separate and rub against the shift fork. Then the fork gets hot = blue color, or damaged. Check all claws in detail.
Crankshaft check: grasp the conrod with the left hand, leaving the small end free and the rest of the shaft hanging free. Hit the small end with the right hand downwards. If you hear a "bling" the big end needs to be replaced. At actual prices it is cheaper to buy a new one. Keep the old for a later rebuild.
Cylinder head: can be machined, (which is done anyway if you switch to 300 ccm, eventually). Keep it.
Ball and bolt: typically someone screws this bolt out for gear oil change and loses the ball and spring in the oil tray. Here a ball with wrong diameter was apparently used. Didn't you have troubles in shifting? Find a tube who's inner diameter is slightly greater than ball diameter, but smaller than the screw. Put the screw on the top and ram the whole to the floor. Maybe the ball comes loose this way. Otherwise these parts are not expensive. By the way, in the articulation in the footrest of the kick starter is the same type of ball
I estimate the cost for new parts (crankshaft, bearings, gaskets, seals, two gearwheels) towards 300 Euro.
While you have the bloc apart, take the edges at the cylinder base out, that hinder you to put a 300 cylinder in later (maybe). Easy done now, bigger problem later. Have some pics to show later.
Carsten

Hello,

So to repair the engine I need the crankshaft ( better buy a new one as it was a bit tricky to get out and I had to use a "bit" of force), shift forks (at least one), gearwheels (I can't say which ones?), bolt and ball, all bearings gaskets and seals.
And of course a new piston, cylinder and a new cylinder head. Or if someone has pictures on the work that has to be done to the head if I choose to upgrade the engine to 300cc, i would be thankful. Also if something has to be done to the engine block in the upgrade process I would be very grateful to know.
We have a small finnish forum for mz but answers there tend to come always too late if they come at all. This forum has been much more help to me.

Pics: here is the casing in original condition


and here reamed to allow up to 77 mm pistons (the machined diameter is 80):

Hello,
Thanks for the pictures, just to be sure the red arrows show the material to be grinded away?

What is the bolt in the same picture, the one shown with the black arrow? I don't have it on my engine...

Maybe with the cylinder head would be easier to buy one that is already made for 300cc engine...

Teemu

red arrows: yes.
This casing is for separate lubrication, the bolt closes the oil inlet where the hose from the Mikuni pump was connected.
So you have an engine without pump, eastern version.

If you want an easy version, buy a new 250 cylinder and new head, and drive. Meanwhile you can buy a 300 piston (not the cheapest, bad quality), let the cylinder drill and hone. By this you lose the centering bord on the top. The cylinder head needs to be turned to the exact piston shape, and the inner diameter enlarged to I guess 50 mm, otherwise the compression is too high. Without centering bord, you need a copper gasket, thickness according to the right squish which you must try.
Then adjust carb setting, and the exhaust is not the best for 300, but you can use it. It revs not higher than the 250, but has a little more torque around 4000 rpm.
Best would be to have a second engine to work on. Depends on how much you're infected by the MZ virus

Hello,

One stupid question: what is gearwheel claw?
With the cylinder I think I'll stick with the 250cc, much easier. Maybe after next seizure get the big block.

Teemu

Hi Teemu,
with claws I mean the parts that interlock between the gearwheels.
Look at the pic up right, you see a rounded edge. This must be replaced, including the opposite wheel.
Carsten

Hello,
Those were the gears that I thought, just was not sure. Is it called schaltrad?

Teemu

Yes, the cog with the groove is the "Schaltrad 3. Gang", the other simple one is called "Zahnrad 3. Gang".
3rd gear is Archille's heel on the big MZ engines.

Hello,
Thanks again. Now it's easier to get right parts. Other part names I got from Reparaturhandbuck fur das MZ-Motorrad ETZ 250. I got a copy of it from a fellow Finnish MZ rider. Also got a copy of spare parts-book in German and English. Quite useful things to own.
Now I have compare prices for the parts and then start re-assembling the engine.
Teemu

For the 300ccm cylinderhead, the form of the combustionchamber in the head depends on the form of the piston. So you have to check the pistons form and than you can have a look here, combustion chamber designer.

Hello,
I started thinking of the easiest and quickest way for getting the bike on road, This option.
The only problem seems to be that the new engine has circuit breaker ignition and my bike has the electric one. Can I put the whole generator assembly from my engine to the new one so that it will work?
Or what would be the easiest solution?
Teemu

Hi Teemu,
1100 Eu for a new engine in GDR original state? New engine sounds good. But probably you got the old seals and DKF bearings inside. And it has probably some original, tolerance-based "flow restrictions" inside (casing - to - cylinder channels and inside the cylinder channels).
The ignition can be changed without problems, only the support plate and the cam need to be changed.
You can even connect the blackbox to the contact, I guess the green wire is it. You have the original electronic ignition with the blackbox beside the battery?

It is difficult to tell, but I would build up the engine by myself. For 1100 Eu you get crankshaft (79-99), SKF bearings (60), seals, 3rd gear (50), screws, a one-row needle pin bearing, reinforced clutch springs, and still pretty much money left.
Work properly, with heating, cooling, not too much liquid seal. Leave the assembled block one week without oil, to allow the seal to harden to the core.
Riding with a self-rebuilt engine is a great feeling
Carsten

Where in the manual can you find that the crankshaft must be 100 degrees when mounting the clutch?? It does not require heat to mount the clutch, most important is to degrease and clean the two contact surfaces and to tighten the nut with required torquevalue.

/Fredrik

Hello
This is what I have heard even in Finland. I think I'll just fix up my engine. Is there any web shop in Germany that anyone recommends? Or are they just the same all.
Teemu

Hello,
It seems to be impossible to find any 251 cylinders and cylinder heads from anywhere. I'm getting a bit bored trying to find these items. Especially as all web-pages are in German and the translationrobots do not know all words. It even looks as some companies sell 251 cylinders but actually don't have them.
Maybe I'll just go and buy a cheap Honda for the summer...

Hello,
Does anyone know how reliable this shop is: shop.
I order stuff for my bike a couple of weeks ago, payed last week and after that nothing. Can't get any replies to my emails. I'm getting a bit worried, I hope there is no reason.
Or should I take a plane to Berlin and pay a visit...
Teemu

100% reliable.

He wasn´t in Berlin the week(-s) before. So I think this could be the reason for the delay.
Give him a call, would be a good idea.

In January I was in Gabors MZ-Laden. He realy exists and works.

Ok.
Just was a bit concerned. I was also a bit late with my orders as summer is coming and bike is still in pieces.
Thanks for the info. Everyone is just warning about web-shops, especially in some Finnish bike forums but I have always got everything I ordered. MZ scene is a bit too small to have any bad dealers I guess.
I'll just have wait then.
Teemu

Give him a call!
Could be also, that there are anyother problems.
Don´t know whats going on with his english expertise... we will see

Hello,
Maybe I'll give him a call later this week. My German is straight from Rammstein lyrics and a few lessons from school back in the 80's so maybe some communication problems could occur.
Teemu

-- Hinzugefügt: 24. May 2010 20:43 --

Reliable, maybe. Fast, definitely not.
I will apologize if I'm wrong.

Alles in ordnung.
Forgot the pentecost on it's affect on everything.

Hello,

I got the parts and I am ready for the engine assembly. Only problem is the bearing shown in the picture. Bearing.
There must be a special too for this bearing but is there any other way to get it out?

Regards
Teemu

There exist some tools for this. But first warm the motorside of good 100 Grad Celsius. Then put it hardly on a wood-workmate. Normaly the Bering fall out.