MZ/MuZ Riders

Hi Guys,

I have a project. An ES250 that has basically been unused since 1983 and subsequently taken apart and stored.

Unfortunately last year it had taken some water damage due to flood, which is evidenced in some places- but not so badly worn in others.

I can't wait to get this project underway, and after sorting out some other problems with other vehicles (now 5 bikes and 3 cars.. :O ) I couldn't stop myself from starting. The difficulty was where..
Anyway, i'm not a good documentarist, nor am I a good picture taker- i'm very much a 'let's just get it done' sort of person, but i'm going to do the best I can here for a bit of fun.

The bits as I picked them up(frame upside down):






So after a cursory look at the engine, thankfully it turns over, and actually has fair compression too! It is obviously my plan to re-build it, but for now that makes me happy. Under the generator we can see that it is very nice and clean.. promising!




After this good news I decided to pressure wash the frame. It is solid, but there is a substantial amount of surface rust. For now just a clean will do. I can get the majority of things in one piece and pay for shipping hopefully for parts in just one go.




But before I did that, I removed the top race and the ball bearings for safe keeping. It must be said that the preivous owner had also kept the lower bearing balls, but unfortunately there were a couple missing. I was thinking about taking apart an old caged bearing but I had none with 1/4" (6.3mm) balls- so here was my first purchase. x24 balls- £1.90. The races themselves are good.




After that quick clean, it is my intention first to put the frame and items (like mudguards, wheels etc) on the bike as one unit, certainly make it easier to manoeuvre around and see what I do and what I do not have.



I start with putting the airbox and fuse (box?) holder in place. They sandwhich around the central air intake of the frame- like other MZ's, the air first passes through the frame. It seems I have a great deal of the parts here. A frame can't be complete without wheels, so whilst I wait for the ball bearings I take apart the drums. Pleasantly surprised with the condition. Also, note the external rubber seals for the open wheel bearings.






Don't forget to lubricate the rear brake pivot shaft and also maks sure the grease nipple accepts grease- this one did after a lot of pressure..! Pleasantly surprised that this shaft wasn't seized as this has been a pain of mine in the past



Front drum (note bearing seal again)


Here is a picture of the internal cable mechanism. So fashionable! The front shoes seem like they are a different material than the rear as they're red as opposed to the usual grey/charcoal colour. I haven't actually looked into whether the shoes are original, but with the small mileage it's likely unless the fronts were changed for brake performance reasons..?



In any case, after the pictures the shoes were disasembled, greased etc.


I spent an AWFUL lot of time on the tap...! It was (mainly the reserve position) COMPLETELY full of what can only be described as a hard putty. But out it came, I have a functioning tap- must be said that a fuel finter is definately on the cards. The tank, although a bit gloopy isn't really rusty. I'm not going to do anything with the inside of that- just keep running it through. Similar thing I did with my 251 which had a much much nastier inside of it's tank.

So as church is still closed I decided to move onto the wheels. For the bearings are seized. It was impossible to get them out by punching on the inner race of the opposit side of the wheel however as the spacer wasn't moving sufficiently enough. So decided to give this little tutorial.

So thus the only real way I could do this was by breaking the cage of the ball bearings.. I did this by using a nail between each of the balls and then removing the cage componants.



Once this is done you can align the balls on one side.



Then using a punch or something, hammer the inner race out.



Remove inner race, and balls. Take the spacer out of the new gap- and that gave access to remove the bearing of the opposit side.
Once this is done there is sufficient lip to then remove the outter race that is still stuck in the initial side. You must be careful to disasemble the correct bearing side, as only one side you can remove the outter race this way- the other side is covered up and will not allow the outter race to come out unless you pulled it out with a press or something- or if you manage to re-assemble the bearing.. Generally- the side with the most slack on the inner spacer is the side you wish to disasemble the bearing on.




So to add to the list, 4x new bearings- 6302 required. Unfortunately the place I last bought (really) cheap bearings at 2x for £1.90 delivered is no longer available. So will have to buy at £1.99 each for cheap UK supplier. I don't mind using cheap bearings on wheels because they are easy to check and replace when required. Not so with engine bearings.

Great project! And it seems you are lucky, it appears to be in quite decent condition. Now I understand this bike has not done many miles at all (less then 10k miles or so), and that shows in things like wear on the brake shoe liners. Btw, watch out with those, they are likely original & may well contain asbestos.
And quite possibly the engine itself will also have very little wear then, let's hope there's no corrosion on the bearings. To what sort of level do you want to restore the bike?

Slick trick on the wheel bearings, but I never really came across that issue, of the spacer giving too little clearance. nevertheless, ta for showing this possibility.

Thanks Puffs- it's not too bad, but I have foudd a few issues along the way. For a start, it looks like the bracket that holds the top part of the left hand side cover on has been ground off! I've asked fellow MZ club members and it does appear to have been removed.. Not sure why.



The mount is supposed to look as such (right click and 'view as' if too large for your computer monitor, as linked from elsewhere):



The bike has according to the clocks, 12,058 miles. The shoes look barely worn so it might be possible they are original. I've got no real plan as of yet but to get the bike together. There are a few parts which I realise I already need to purchase. Removing the bearings like I did seemed like the only viable way with my tools to be able to remove them.


I have assembled the bike more, including the wiring and placing the headlamp shell and tank and seat. Another thing worth noting is one of the seat attachment brackets is quite mashed up. It should work, but it might need reshaping and welding in the future.



The wiring diagramme (in the including service manual) was of help, but it was a little confusing, for although the wires are colour coded, with writing (in german), the wires are coloured in the diagramme according to what type of job they do, ie Ignition, Lights, charging. But I go them all in the end I think. The bike doesn't come with indicators, so although they're somewhat wired up, those wires obviously won't have anything to do. Still it's good to keep them in the bike maybe for the future.



I did have to replace the ignition switch with one I had spare because some of the spade terminals had come undone where the male connection is riveted to the switch. No big deal though. Pictured is the old switch, with two less terminals which have come undone. I had to remove the cover to gain access to the screws for the switch- it is very very soft and maluable metal so that's a tiny bit deformed but it's not too bad- should be able to get it into shape again..



I'm not sure if the electrics are fully where they are supposed to be, but I've yet to buy a battery to see. I suppose that's one of my next purchases.

Right, so now you're a Rundlampenschweinchenliebhaber! (=aficionado of piglets with that type of headlight)

Bracket - bummer. You'd have to make something then. Is that LH cover also the air box, as in later models?

With 12k miles it should still have little mechanical wear. Consider to re-spoke the wheels (with stainless spokes). Not only is it structural, also it's the perfect start to really clean up a bike.

By my book no indicators is good and in the proper style. Indicators are ugly. Just use your hands as required!

Before doing-up the electrics & investing in it, maybe there's another choice to be made: to EI or not?

Yes, it's a funny design of bike really...

Yes, i'll have to find the dimentions of the bracket that should be there and fabricate and weld something up.. Annoying, but oh well. Even if I did get it together and running, it wouldn't necessarily be on the road immedately. But, at least with a battery strap, everything would be secure. The rubber battery strap that came on the bike fell apart in my hands obviously.. Though I am very good at zip tie fixings.. Yes the airbox is on the RHS, and the electrics behind the LHS cover. Quite the reverse from later (TS250) models.

I did pump up the old tyres- definitely will be replaced at some point. One of the wheels escaped a load of water from where it could as it was being pumped up. But it looks like they're both holding air. But at current no immediatness just for rolling it around, and possibly using it up and down the lane for testing (when I get to that point). I have spare tyres but none of them are 16". I also want to just see what they like in the standard tyre size. I might like it more with larger or smaller tyres- not sure yet. Standard is 3.25x16 front, 3.5x16 rear- but it has a 3x16 at the front, which apparently according to the official service manual is explicitly stated as a possible permissible size. It also comes down to what I can get for the right price too.. The 3x16 and 3.25x16 are very limited- and the only tyres I can find are expensive known brands, which never impress me. I can likely get a Duro HF319 for the rear though (same as my 251). I'll have to just do some searching around. And I hear you about the spokes. The front wheel is definately better than the rear. We'll cross that bridge when we come to it, I think.

The bike has the wiring for the indicators, but they are placed on the end of the handlebars traditionally. Odd, but I suppose with only one bulb per side actually 'blinking' that saves some bulb performance...

I am not going to use electronic ignition unless the bike has issues.. I would like to use the points and standard generator. But if that causes problems down the line, I can use contactless ignition just like my 251 has- £60 for that.

I have just purchased a battery. The model number requirement means that there isn't a lot of choice. But in the end, bought a standard Lead Acid battery (better for old charging systems that vary wildly in load) for £27.

I took the carb apart last night, the outside looks nice- the inside is not.. The carb body is soaking in petrol at the minute- the slide is stuck! And once I get it out i'll have to take a picture, because it's more of a sleeve type slide as opposed to a cylinder. It's very interesting.






I took the head and barrel off- the piston seems like it has great clearance still within the barrel and moves nicely. The barrel lining is not rusty at all- of course there is scuffing on the piston and barrel but they look like typical wear and tear (maybe run with no/little oil).






But on the crank is a mix of oily water. Some indeed did tip out, but it was clean water. Obviously I cannot see the bearings but everything turns nicely and without notching.





As you can see in the video, there seems to be a lot of side to side movement on the conrod bearing. It seems rather excessive- of course with the piston in place the conrod shouldn't move side to side like this so it makes me wonder how this has happened or whether it's been rebuilt in the past (the intact flat head screw heads suggest not..)

https://www.youtube.com/watch?v=oOD2Pys3PsU


So i'm not too sure what to do at this point. Part of me wants to put it all together and in the bike and just see how it sounds. And I can go from there. It does seem like shims or something are mising from the main conrod bearing though..



I've started to make a list of things I need that will probably be bought from both MZ-B and Ost2Rad. Ost2Rad seem to have the very bracket that has been cut from my frame..

https://www.ost2rad.com/MZ-Spare-Parts/ ... s-250.html

Maybe the original clip had been bent a bit too often and broke off? But it's interesting to see you can just buy these - there seems to be a market for them, so apparently it happens more often...

That carb looks very yukki... Could WD40 help?

While the bore looks reasonable (for 12k mi), there are quite some marks on the piston, and water in the crankcase is bad news. That brown colour might be caused by rust.

That sideways clearance looks like a lot. I do not know what the book says, but sideways clearance is not normally a problem. Normally radial clearance is the issue. How's that small end? Bronze bush? (Y --> rich premix.)

My view on your questions: I do not know how a shim could go missing, I don't think it can. So it probably had this sideways clearance from day 1, and I don't think the sideways clearance is an issue. But if it has (pitted) corrosion on any of the bearings, that is the issue. It will run, and you'll think it's OK, but then, when you least want it to happen, a bearing will fail on you and you'll need to find a trailer to get the bike home. It is not a certainty this will happen, but with rusty water in the crankcase, it surely is a possibility. You can play the chances, but the structural approach would be a full overhaul.

Lovely bike, Great project. I look forward to seeing it develop

But is BM a rundlampenschweinchenliebhaben?
Rundlampe means round light, which suggests to me it refers to owners of the mark 1 ES rather than the Mark 2 with the square headlight shell.
In any case, congratulations on a great project, which I am following with interest. But don't spend too much time in the workshop in this weather.

Ta Dave, I was wondering who would be the first to correct me... I just had to use the word!

I do like the mark 1 ES175/250 but I do believe these trophies are considered mk2's. It even says it on the rear mudguard- ES250/2 (the /1's were I believe the original iteration later denoted /1 to distinguish- but this is a '74 registered bike and they definately didn't make the mk1's that late). Of course this is called the 'trophy' series as a self congratulation for their offroad prowess in the 60's, and the tank cap also has in it the years they won. That said, yes the lamp is round, but the shell is square'ish' more like a kind of Trapezoid. As you'll see.


Anyway, my battery arrived. And I did realise my charger is 12v only. None of my close living friends have 6v capacity chargers-my dad has one but he's 30 miles away. So I wired up a 6v 25w globe (TS185 headlamp bulb) inline with the charger. When the voltage got to around 7.3v according to the volt meter, it plateaued and I disconnected it. The battery is charged now. The battery isn't quite like it should be, the negative terminal is on the frame side instead of outside, so that's a bit annoying, but not necessarily an issue considering it's the earth terminal.




I also got my ball bearings.. But I made an error! I should have ordered 2x sets of 24, instead of just the 1 set. I realised this after installing the 22 new balls at the bottom race and then realising I had made my calculation error. So.. I re-used the best of the original balls that were available (41) in the top race.. Thinking they would be the easiest to replace if I did decide to buy more. The handlebar was also installed, and the head nut knocked on. Whilst in the process, all the remaining original balls fell onto the floor (I left them on the seat of the bike), I haven't found them all, so I might be finding the lost ones for a while to come!


With the battery charged- I hooked it up. Two things are an issue, the rear lamp and the brake both light up as they should, but none of the headlamp (or pilot lamp at the front(or speedo backligh)) work. I'm pretty damn sure my wiring is correct. Of course there could be an issue with the wiring itself- corrosion etc. Could be an earth issue. I know for a fact the bulb filaments DO light directly with battery. I'm pretty sure the headlamp bulb is DC (hence why they had good lights back then compared to competitors) and even if it wasn't, the pilot light should come on for the purposes of the key being put in the parking position). But I noticed my spare ignition switch wasn't completely tight on the key and the indicator lights (the charge and neutral switch light which did work) were fading and not entirely bright consistently and would dim/bright depending on slightest key position. So I likely need a new switch. I do actually recall now that I removed that switch from a bike because it seemed like it didn't make proper connections. Easy fix for that though. Buy another! The horn doesn't work either -that goes to the ignition switch too.. but I haven't actually tested it directly with the battery so could just be dead.
A small win- one of the items on my to buy list is a battery hold down, but it seems I have one. I bought one years ago thinking it would fit my ETZ but it didn't, it's the exact one I need for this bike however - woop! Looks like I need a new fuse box too as the fuse holder has broken on the earth. But that's okay for now, I can just connect the earth wires directly together- not entirely sure why the earths had fuses as well as positive, but I have actually blown the negative before now on my ETZ..!




Something is weird with the above.. there are three prongs on the headlamp back shell that fit into recesses in the holder. And this is the only way it can be put in.. Odd.. because as you can see the reflection is completely off... I would say the glass has maybe rotated but the bulb holder itself seems upside down too, which doesn't seem right. It's not loose in the bowl though. The bowl is almost bare of silver anyway, so will have to think about this one!



What with the carb soaking in petrol and all it's jets for 2 days, I got out pretty much all of the sludge, and what's more the stuck main slide just fell straight out.. Good start! All the jets then got the compressor and cleared out nicely too- the idle jet took a bit more pressure at around 110psi to get it clear though after another soaking. But that's it.. It's all clean enough that I can see nice round sunlight through the holes (and the orifices of the carb too seem pretty cleared out) and here is everything layed out:




And assembled, with correct float height:





A few things I noticed on the carb. There is no idle speed adjustement- this is done by tensioning the throttle cable apparently.. But there are some inconsistencies with my jetting. The main jet is 120 instead of 107, and the float valve jet is 20 instead of 18 (though that really isn't an issue). The needle itself looks like the tip has been chipped slightly/broken off a bit. So new jets/needle may very well be required anyway. That said, I'd always plan to buy a needle and keep it in my spares boxes, for just the occasion that it breaks, though it does have a lot more girth than ETZ main needles, i'd say.

My wheel bearings 'should' come to-day, so it will be nice to finally have the bike standing up and not on it's belly like some seal. Dave47- the weather is very nice indeed yes, I tend to work in the late evenings when the baby has gone to bed and it is cooler..

Some comments:
- If you don't have a 6V charger you could consider to use one of those small general ones, but do monitor the voltage & cut it off at 7.0-7.4V or so. Some of those also go to 8-9-10V in the absence of load. The voltage drop over a bulb (or R) depends on the current (so it'll continue to charge go to very hight V, typically 14-15V for a 12V charger).
- Good job on that carb!
Odd that the idle is adjusted by cable tension... Bend the cable (fi by moving the handlebar) and the tension increases...??

On my question on EI, electronic ignition, I think you are right. A bike like this should have the original points ignition, which also still works fine on my ETZ. But here, for the ES, there are even more reasons, as it has an advance system:
At higher revs the weights move outwards, and rotate the cam a little. This advances the ignition timing dependent on the RPM (to some 3.3mm bTDC max), while at low RPM the timing is later. This way, this ignition optimises the engines efficiency, and reduces the tendency to kick back during starting. From another thread, I don't think something like that is available in electronic ignitions, for the MZ, and loosing that would be a pity.

The bearings for the wheels finally came.. So I couldn't wait to install them. They are cheap cheap Chinese/Indian made (some random company called LYC), and two of them were a bit gritty(?) out of the bag. They are not sealed in a box or had bags, and they just had storage oil for rust protection. You get what you pay for. I'm not complaining, I knew they would be poor, but I'm just stating facts. I knew what i'd be getting, and it's something that doesn't concern me when it comes to wheel bearings. That said: engine bearings are a different matter though! Those I won't cheap out on! So after weashing them in petrol I greased them up and punched them into the wheels (I love punching wheel bearings in/out of wheels- such a good feeling). If anyone is interesting this make of bearings seem to identify their own model numbers (so these bearings are 302e, no 6302). http://www.lycbearings.com/lyccatalog.pdf


I did have a look at the bearing(s) in the chain sprocket carrier- and it(they?) were definately grumbly so will also be replacing it(them)- but that can be done later (and for good quality ones too, as from experience they can be a bit more tiresome to remove). Looks like the rear sprocket carrier has only one bearing as opposed to two that the later bikes seem to have. I may even have one spare in my boxes of unused or mis-purchased bearings. The back end is just mocked up anyway (for manoeuvering) as I don't have a chain yet either.
What with the disasembly of two of the old bearings, having the outter race to hand to install the news ones of course makes it a lot more seamless!




And mounted them onto the bike. I didn't really do anything with the brake drums other than brush them down a bit. In my experience, just using them will do most of the cleaning up. I had much much worse rust inside the drum of a Suzuki TS185 that just by using cleared it up- I didn't even have to replace the shoes after but for general wear- as they didn't get eaten up. So that's my plan there.. With a good spin, you can see the wheels seem pretty straight and don't seem to be too unbalanced either, actually.

Then I got to work with the electrics again. There everything seemed fine still, but I connected the coil and it's wiring, and also installed the engine. The bottom mount bolt directly on these rubbers.. Very interesting, I will be replacing these as previously mentioned as they are torn and broken, but held up just enough for me to install the engine! I had to bodge the HT cap connection as the bits inside the one still connected to the coil had disintegrated. I simply cut away the sheeth of the wire and did it old fashioned type and curled the HT lead contact around the spark plug and screwed it down with the adapter that they sometimes come with for different cap connection design. Had to borrow the sparkie from my ETZ.





After a bit more faffing by putting on the exhaust, we have last nights product:




I put some petrol in the carb and in the tank and pulled the choke and actuated the throttle cable with pliers and it runs! There was some popping and some hesitation, and some general grumpiness from an engine that hasn't run in many years, but it started readily and easily actually. I know running this engine could pose to be a risk to some, and things can also develop, but it sounded good and was strong, for now. There is a fuel supply issue. I will need to swill around that tank now that it had a litre of petrol in it, I think general sludge has been carried down and now collected around the reserve position on the tap. The plastic spigot on the tap is also a bit funny. Will have to replace that. Ost2Rad have metal replacements for 2 euros 10. ...hmm

I'd say it might idle but for the fuel supply issue.


Now I need to work out how the throttle assembly goes together... and whether I have all the parts to make it work, because I'm not actually entirely convinced of that. It looks like I do from the parts listing diagrammes on the Internet, but I can't quite work out how it goes together yet. It would be easier to use than pliers though whilst trying to juggle other things. I'm not an octopus! The throttle assembly is an inside the bar arrangement so it's not that I have spares on me. Though I might be able to use an external throttle assembly to get me by for now.

I didn't quite manage to get an accurate reading on the battery whilst the bike was running, in order to work out whether it was charging or not. So we'll have to come back to that after the bike can run on it's own without intervention.



Puffs: Yes, I used a few different bulbs at first before going ahead with it fully to give me initial readings that I found best bulb. It started at 5.8 or something, and gradually rose and I turned it off at 7.5. Any more than that is probably considered overcharging anyway. I was under the impression I might end up doing this a few times in shorter bursts but in the end it didn't seem necessary as at the end of the charge when I turned it off I got 6.28v
Yes: That is the thing, electronic ignition has good and bad points.

Good:
no maintenance,
reliable.
Normally quite cheap enough!

Bad:
No adjustability between cylinders on bikes with multi-point system,
if it breaks on you, you're stuck! (points you can bodge something),
no ignition advance curve.

You're going very quick! And that pic after your first assembly does give a good impression of the bike - it's a true DDR icon. And it runs... congratulations! Not a big risk there, IMO, but bearings may fail on you in due time.

EDIT: when looking in the documentation, I saw that this engine actually lubricates the main bearings with gear oil, so that reduces the risk of those having corrosion issues. Of course there are still the conrod bearings (both needle bearings) that were open to humidity.

If you run that bike inside: ventilate! Carbon monoxide is a true health risk.

In the absence of a working throttle handle, can't you just pull the inner cable? That should also lift the throttle.

On using filament bulbs as a resistivity (R), they are a bit funny. When they do their thing, shine & emit light, that filament is very hot, and the resistivity of metals normally increases with temperature. So in operation, a 6V 24W bulb does a current I = 4A (P = 24W = V * I), hence has a R = 1.5Ω (V = I * R). But when it does not shine, so when the filament is colder, you'll find the R to be lower.

On electronic ignitions, IMO their biggest advantage is more accurate ignition timing. With points, the timing can wander a bit, due to vibrations, particularly at high revs. Now the ES 250/2 is not quite high revving:But still, wandering ignition timing is mentioned as a possible disadvantage of that mechanical advancer, particularly if it has too much clearance (which it shouldn't have in your case, with 12k mi). Check it can move freely, so that it advances properly.