New ES250 Trophy Project!

[Puffs]

Yes I read yours BM; some comments:

- when you put something (like a washer) on the inside of an air box, be very vigilant that is stays there, and will not enter into the intake. And cause destruction.

- if you have another (conventional) throttle handle, I'd give that a try, to see if you like that better. The ES's system with the 2 opposing springs is very ingenious and slick, may avoid surging & all that, but I see MZ too moved away from it in later models.

- Yes the ETZ's alu air box is very well made. And in fact the entire aspiration tract is, IMO, very well made.

- On the 'e) Cover sealing...' issue, what do any of the other ES manuals say?

- Right, so you get 2 lights telling you exactly the same... Maybe just take one out?

David, if your comment is suggesting that two stroke bikes are difficult, it is not entirely fair: Blurredman is dealing with a 50 year old bike assembled from parts, not necessarily complete, and which have also been in a flood. OK, he runs into a few issues... For me the lesson is: if you want easy, don't buy such a basket case. But I think he's doing all right!

[Blurredman]

Regarding the idiot lights. It seems I need to connect one (or two) bulbs to item 54 on the main ignition switch. The neutral light only has one connection, the charge light has the connection to the bulb and one on the side that is presumably earth- so.. I guess either the lamp connection or the side connection (I suppose it doesn't matter) just needs a small length of wire to the 54 terminal on the ign. switch. This will replace the small section of loom that does the indicators, that will bridge the connection that is now missing.

Item 23 are the idiot lights. L is the neutral light, M is the charge/indicator light. As you can see with the wiring the switch is 'switched' to ign on, and power will then go to the charge light. The neutral light will light when the ground contact is made in the gearbox, and the charge light will at how it should based on the voltage that it sees coming from the 61 terminal on the voltage regulator. I think it is just like a typical alternator discharge light. The discharge light is normally ON. Then when the engine is running, the regulator senses that it is being charged and the light goes OFF. It will light dimmly or fully when there is excessive draw. So yes I should just need to bridge the connection from ign. switch to the charge lamp.




EDIT: I'm getting a little confused actually regarding this. Because the attached image shows it connecting to 54? But in the official manual it states 15. I suppose they both will operate ignition live so It could be either one I suppose (?) Oh well- I'll experiment and see.
EDIT: Yes Dave, that is true I think you're corredt. I think terminals 54 and 15 are conjoined. There is no way that all the items the ignition on condition would connect too all that it does without them being one unit. The original manual has the two bubbles 15/54 touching like they are conjoined. What's more, on the TS125 6v diagramme, it shows a different wiring whereby the indicators are coming off terminal 54 as opposed to 15 and other such things. This is why 15/54 is only represented as a single square in the 'switch54' picture. As you can see, there is a live connection from terminal 61 to the charge light and thus the voltage regulator. I've heard these 'emergency positions' don't even work.. There are some hills on the way home.. Maybe i'll experiment with what that does. But- I have a full battery so might be pointless.
As attached.

[dave47]

I don't envy you working from the horrible MZ wiring diagrams. The ETZ circuit diagrams were much better.
Both control lights are probably fed 6v by a single wire from terminal 15/54 on the ignition switch. As you say, the other wire from the neutral light goes to the neutral switch and then to earth when in neutral, and the other wire from the charging light goes to terminal 61 on the voltage regulator.
Two complications are:
1. There may be another wire from the charging light to terminal 61 on the igition switch. This is part of the emergency, flat battery feature, which is not really necessary in my opinion.
2. The charging light doubles as an indicator warning light, also unnecessary if you have no indicators.

[Blurredman]

Okay guys.

So yes I did manage to do some things last night. I put a bridge wire between 15/54 and the vacant spade terminal on the charge lamp (that the indicator loom would wire to) and now both lights act independantly. Charge light disapears when the engine is started (but equally comes on dimmly when at a low idle- so that's good), and the neutral light acts as it should. Good! Thanks Dave.
On the way home from work last night I did indeed try the 'emergency position'. in 2nd gear the bike was reluctant but it did fire, going downhill. Then switched to normal ignition. But.. As mentioned- the battery is already charged anyway so not sure that is any test to read into any outcome.


I took the airbox completely off the bike and put the same 1/2 washeres (drilled out hole in the centre though with 7.5mm drill bit), and installed them between airbox and electrical 'carrier' bracket. The book calls for 2mm gap- these are 4mm washers, but with a bit of squish it seems to be air tight (I carb sprayed everything). And now I think the only area of concern is the top of the carburettor- not sure if this is where the cable enters the adjuster nut, or the gap between screw down cap and the retention piece for the cable itself.





I had a look at my spares, and something I came to realise is that there is no 28mm carb from the MZ line with a built in idle adjustment screw on the slide- the TS uses 30mm, and the ETS uses the same carburettor as this Trophy. The cable tension is set by the carb but also seemingly the throttle clamp with a tapped cable entrance hole - But how is slack kept for movement of the bars, compared to the requirement that the cable needs to be tentioned in order to keep the slide height?

I have a throttle tube. I have a throttle clamp. I didn't get around to putting an ETZ cable on. But I'm not sure all of this would particularly solve my problem, esspecially considering the above.. The bike labours when it's idling.. So I adjust the cable adjuster on the carburettor and get the idle up a bit. Which is great- then I give a test rev and the bike continues to stay revved up or is extremely low to get back down to an acceptable idle. It's infuriating. What is this indicitive of? I think i've got rid of (except the top of the carb) all the air leaks possible.

[Puffs]

Good on the instrument lights!

On the idling, I'm just wondering: for these bikes they specify quite an advanced timing, up to 3.3mm bTDC. But you do not have the standard retarder. As discussed earlier, that retarder was there mainly to avoid kick-back during starting, with that advanced timing. Although Guesi earlier said otherwise, possibly it would still retard near idling revs? And thus make it idle better? At higher revs an advanced timing is/can be desirable, but at low revs the engine starts to run irregular, or maybe what you call 'labouring'.

Not sure if this makes any sense, but if you still have it at 3.0mm bTDC, you could try 2.7mm bTDC or so & see if that makes any difference.

[Blurredman]

Hi guys, just a quick update.

I have finally solved all the air leaks. The last one was seemingly the fact that I was missing a gasket that gets placed beneath the main slide cap. I implemented a conveniently sized Honda CX500 inlet manifold O-ring in order to get around this. The idle is much better in the sense that it doesn't lobe so much at one minute, but rev highly the next - but alas, with hours of reading on-line this is simply a problem inherrent with the design of such a throttle assembly.

It is apparent that MZ thought that the possibility of 'retarding' the what is constantly complained about 'surging' by users by rolling the throttle forwards and closing the main slide, outweighted the cons of such a system namely this idle problem.

There are a few steps forward. You can send off or buy a replacement BVF 28n carb whereby a machinist can implement a an adjustable rod that prevents the slide closing too much and gives a reliable point where the slide closes at - here is an example of what I mean: https://www-simantik-de.translate.goog/mz-bfv-vergaser-regenerieren.shtml?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=en-GB&_x_tr_sch=http, or indeed buy replacement carburettors such that have already been tried and tested on this forum from Mikuni and PWK or the very documented copies of said carbs etc.

However my preferred forward option might be to buy a replacement es250 inlet (or do this to my own if I cannot) and bore out slightly the clamp around the carburettor (and possibly the outter face of the carb air inlet for the air tube to fit over it) and fit a BVF 30N2 or 30N3 carburettor - if the 30mm carbs don't natively fit in the ES manifold. The TS250 inlet works too and is a straight fit but of course won't have facility for carburettor cover. So therefore a 30N2-3 to 30N2-5 would be best as they do seem slightly smaller physically and may fit within the carburettor cover if I am trying to look original. The benefit of these carburettors of course is that they are more original yes, but they implement a stop screw for idle (in the case of the 30n3-1 a bypass air screw instead). But also the jetting is still very close and easy (and cheap) to find.

This of course brings up the question of throttle handle however- I would prefer to once again use the sleak design of the internally drawn throttle tube slide. But if this isn't a possibility it's easy enough (but not as nice looking) as the TS/ETZ throttle clamp and tube we all know well. This option might mainly depend on the throttle cable length required.

So, what I have said above is indeed in my mind something that I might want to do. However this is likely something i'll not implement until some un-dated future. At the minute I am quite happy (even if the bike is a bit more engaging to ride therefore) in using the bike for leisurely rides in the country, over the more challenging and time dependant riding conditions of say commuting.
At the minute therefore the main running complaints (which should be resolved with the above mentioned replacement carburettor router) are these:

1) When you brake with the front brake, you naturally roll the throttle forward slightly - this dips the idle and has the potential to stall. This is annoying when stopping at junctions or traffic, because as well as balancing the rear brake you have to keep a control on the throttle- and what with the heavier clutch, means not only a straining left hand, but also a straining right hand.
2) If you're 'pushing on' then it takes an awful long time for the rpm to come back down between changing gears. This is what encourages gear crunch and also missing gears. It's incredibly difficult even with sedate riding to be silent on the first point. The way around this however is to: Push the throttle forward and close the slide. This brings the rpm down quick enough to not look silly. Then change gear, and pull back on throttle. Which is fine enough to get by- but it is a slow process, and you lose momentum and speed and can easily find yourself downshifting because time has gone too slowly and you no longer have torque to use the higher gear you previously selected.

Regarding point 2: It has been said to me that the crank is possibly heavier than TS/ETZ, but it is certainly the case that the clutch is heavier- the heavier items may be the reason for the rpm to be slow to reduce- but at the minute the main needle is on position 3. It might be advantageous to richen the mixture and use position 4. This will also give a bit of better torque at lower RPM. This is dependant on spark plug condition anyway, but the richening of the system may make the usability of the system easier at the cost of potentially burning spark plugs out before the stated 6k mile/10,000km renewal time interval.
As a back up perhaps to my thought that the bike is perhaps running lean, the bike does take a while of time and a lot of intervention with the choke and throttle after starting in order to be comfortable to try and allow the bike to idle (as much as it can) on it's own, and then thus ride away. It shouldn't really require so much molly-coddling. So what with hopefully easier starting, the richening by one notch should bring the RPM down quicker between gear changes


A side note is that what with my extended experience of soley using the rear brake for controlling stopping at junctions (and for lighting up the brake light- remember, the brake switch is only on the rear wheel on this model), it is quite aparent that the rear wheel is out of round to a degree. Whether this is a warped drum or loose spokes that can rectify this I haven't looked into yet but that is the only real drivability issue other than the carburettor issues mentioned that I can think of. I did take the both wheels off recently to check that the rust was being removed from the lining, and whilst the front drum lining is nice and shiny (and the brake doesn't pulse so seems nice and round) the rear was still a little bit rusty. It's possible this might be the issue still on the rear wheel, but if that's the case only using the vehicle might solve this. But the pulse effect is so that I don't think this is actually the problem particularly.

I must say it is a culture shock (??) to experience the four speed transmission. As much as the torque curve is forgiving and gives an elastic sort of feel to the vehicle, it must be said that i'm not used to being in 2nd gear at 35mph when trying to get up a hill without hindering vehicles behind..

It must be borne in mind however that I've only covered 170 miles (indeed the bike went into reserve on my last run but I didn't fill it up) which really isn't much for getting problems out of the running/riding of a bike that has been in boxes since the mid 80's. One positive is that the speedometer hasn't 'frozen' since I fixed it the 2nd time. And I have not had any electrical problems at all- other than the fact that the brake light doesn't light at all/very well at low rpm (idling)- works fine otherwise.
I am keen however also to see what sort of MPG the bike gets. Obviously this first tank has been a lot of carburettor tuning (whilst riding) so it will be off, but I will be interested to know if the bike in the future achieves the 70-80MPG average that people talk about with the ES/TS motors as opposed to the constant and seemingly un-variable average of 60MPG that both my ETZ models have.

https://www.fuelly.com/motorcycle/mz/etz_250/1987/blurredman/158285

https://www.fuelly.com/motorcycle/mz/etz_251/1990/blurredman/446527

[dave47]

I don't see that a BVF 30N2 would solve the problem. Obviously its an advantage to have a separate air slide stop screw. It makes adjustment easier and reduces the effect of handlebar movement, but its still a primitive carb. Most Supa5 owners still found they had to choose between "no idle" or rough running on a closed throttle, although some said they had this beaten.

[breakwellmz]

Don`t know whether you`ve seen this - viewtopic.php?f=5&t=8967&hilit=+boost+bottle

[Andy_C]

"Most Supa5 owners still found they had to choose between "no idle" or rough running on a closed throttle, although some said they had this beaten."

I am one of those who has it beaten on my Supa 5, as some of you now it took me ages to get it running anyway, but it seems to idle just fine and reliably at about 1200 RPM, all I did was fiddle with the air screw. I started at the "recommended" setting and adjusted it until I got a reliable idle. Standard carb by the way.

[Blurredman]

Thanks guys

The ETZ models (the 250's, the 251's had 30N3-1), have 30n2's, specifically the 30n2-5. The bikes I have and have worked on including my brother's and my own all have a nice tick over at 1200/1300rpm.
I don't know why people complain about them so much? I find a lot of people when talking about MZ's pass on lots of myths without personal experience with such comments as 'MZ's weren't meant to idle' et etc. And, in a way that I don't mean to offend, are these people simply screwing in and out and not properly hearing what the bike is doing and being methodical about it? Or is the carburettor genuinely worn?

A lot of people complain about worn carburettors on their bikes these days with only 20 or 30 thousand miles on, but when these vehicles were used earnestly in all weathers and had some serious miles on and not the weekend bike they seem to have become in certain circles, they seemed to run fine enough of their original carburettors. I for one try my best to fix the original items on my vehicles and try and disprove the thought that BVF's with 30k are beyond it without proper process of thought and elimination of possible causes Or maybe i'm just cheap?- or simply resolute in my experiments...


The TS250 has the 30n2-3 carb. It is true it has a smaller jet than the 30n2-5, but the set pilot screw is also meant to be further out by half a turn than the 30n2-5 carb. I wouldn't want my bike not to idle, and having lived a long time with the surging that lots of MZ owners complain about (and I honestly don't even take notice of it anymore), I wouldn't be tuning the carburettor in such a way that the bike wouldn't idle to eliminate said surging. I'll put money on it...... I gaurentee if I fitted a 30n2-3 or 30n2-5 carburettor, that I could make this bike idle nicely at 1,200-1,300 rpm

Just for my own curiosity I've filled up the bike and got 60mpg..
https://www.fuelly.com/motorcycle/mz/es ... an/1105224

As of tonight the main needle is on the fourth position, and the pilot screw is at 2 turns out. This much reduces the rpm 'hang' whilst changing gears and makes the bike nicer to ride in general- idle aside.

But yes- when I get time to experiment with my spare 30n2.5 carb, that will be my start for investigation into possible alternatives.

[Puffs]

On surging, I think you're right. My ETZ251 does it a bit, but it doesn't bother me. If need be, on long descents I pull the clutch, as you should anyway with a pre-mixed two stroke (for lubrication). The idle is fine, and it has the original BVF 30 N 3-1, and after close to 40k miles all that had was a bit of work on the fuel valve.

I tried a Chinese Keihin clone, which worked well too. With that carb the surging may have been a bit less, but I still put the BVF back. Btw, the 634 also runs fine with the original Jikov, which is indeed a bit more primitive. But I think in the end all carbs are just a venturi with some jets and a tapered needle; if you get the jetting right the bike should run fine with the original carb. Unless of course it has significant wear (it might not be original and have done more than 12k miles).

I suppose you mean 4th from the top, so the needle gets a bit higher up & a bit richer. The book says 3 to 4, 4 for running in. Of course with DDR fuel of those days. Maybe do a proper plug chop to see if your main shouldn't be bigger, or just try a size up & see how it runs with that.

[dave47]

I've read the link given by bm and notice that the author uses his ES with a Bing, while the skillfully modified BVF is as yet untested. He gives various reasons for the failure of the cable limited airslide to give a reliable tickover, such as cable wear, temperature changes etc, but these would have no effect in the short term. If the idle is set with a hot engine, and the handlebars straight ahead, why should the cable be any less effective than a stop screw?
The TS125/150 carb uses the same system and people don't complain that won't idle, or do they?
Why does it matter anyway? The MZ250 crankshaft is designed to keep spinning by flywheel inertia, so its hardly likely to die on you, if you blip the throttle once in a while.

[Blurredman]

Did a quick (well it took 2.5 hours) 45 mile ride to-day. Bike behaved well with no issues. I took a couple of tools with me in order to do some bits and bobs. I'm happy foremost with the needle being in position 4 (from the top) and the idle circuit being at 2 turns. This does feel the best position for the torque application. And with the idle circuit at that specific position that revs between gear changes are much reduced.

With some very fine tune adjustments the bike isn't too bad at idle now- it's acceptable enough that it doesn't require my attention really anymore. I just also have to get used to not rolling the throttle forward when using the front brake and it's pretty happy with that.

I'm pretty happy to just leave it here at this point and enjoy the bike for what it is. I'm actually getting a bit more used to the vehicle and how it operates and I am really enjoying it. Just wish I had a mirror... Can anyone help me there?

Anyway, that's all I can say really. For the most part this thread is finished at this stage. The bike is together, it is re-built, it is running (and decently now) so unless I make major changes or have specific problems or plans then i'll say the bike is done for now- Though obviously happy to hear other people's opinions and pointers etc. Thanks everyone for your input.

Anyway.. Here are some really bad pictures for fun, with thick fog in the distance. As you can perhaps see by the bit of exhaust smoke- this is idling. The bike really struggled to get up some of the very steep hills on this ride to-day. Had to stop a few times and take a good run up to get up some of the inclines!

https://www.google.co.uk/maps/@51.84020 ... 384!8i8192

[ashthetash]

Mileage for maintenance: things like chain & points (or in fact: most) you do as required, and for the rest you record the fuel you use. As you know roughly how much it uses, it's an indication of the distance done. Taking a speedo apart is not easy, I think.

Does the current behaviour of its mileometer cast doubts on the mileage the bike has done? Not that it matters, obviously.

I'm pretty sure you should have a genuine mileage. I don't recall any problems with the mileometer prior to the bike going into storage.

[Blurredman]

Bit of an update here, as really there isn't too much that has been needed to be done in terms of drivability, or if there are I will get to them in time, but i've done 500 miles now and these two points are getting on my nerves:


After doing some practicing of (MIG) welding, I finally got around to fixing two issues that was wrong with the bike that required welding.

Firstly, the upper mount bracket for the left hand side side panel. After getting the dimensions from Dirtsurfer (thanks), I used the spare metal lid of a VCR player I had kept. It's a bit thin at only 0.5mm, but I other than being a bit of a problem to weld, the integrity of the panel bracket doesn't need to be too strong really. I might come back to this further down the line, but for now I am happy enough. It's been painted since the picture, and sorry for a picture of bad welds with too thin a metal, but I'm a beginer and as I have said I don't mind too much at this stage- it can easily be rectified and re-created if required in the future. I couldn't replicate the original look of the original bracket but that's okay for now. It looks better with paint on



A bit of paint makes it look better...




The second issue was a split and broken open front seat mount. I don't have a before picture, but after metal manipulation and some welding of the crack/split we have a nice and secure mount and flat too. Once again also obviously painted after the picture was taken.