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MZ ETZ 125cc, bike of 1993 manufacture.
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Mags 1
Northamptonshire.
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May 8, 2019 - 10:22 pm
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Four now on the road and at least several in bits.

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Mags 1
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May 11, 2019 - 12:33 am
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I have the full rights to reproduce my article wherever I wish, if anyone is wondering, the text had disappeared when I first looked tonight.

Four now on the road and at least several in bits.

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Mags 1
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May 13, 2019 - 11:06 am
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I've got over quite a few faults with this bike already, I've got a new V5 in my own name for it, but not taken on public roads yet, solved a few issues and maybe created others, a long time thing that irritated me every time I tried to get engine going was rear parking light constantly glowing, not sure if it was an MOT failure, but front brake lever wasn't operating the brake light at all and the rear only occasionally.

I took the headlight off to find the front parking bulb blown, putting the voltmeter across the contacts I found 12 volts there, which immediately made me realise that bie probably uses the parking lights on in the daytime as a safety feature, but don't have a handbook to confirm that, I always think that you need parts book, handbook and a good workshop manual when carrying such work on any bike, not knowing what the normal running conditions of bike are can leave you in the dark - literally...

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I put fresh chemical salts into the ultrasonic cleaner and plenty of water to fill it right up, carb also has been playing up, almost emptying what little fuel I left in tank overnight onto shed floor.

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The dirt was rolling out within minutes.

Four now on the road and at least several in bits.

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Mags 1
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May 15, 2019 - 11:16 pm
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Carb cleaned up a treat, but something wasn't right, old gasket finally tore as I absent mindedly caught it with the screwdriver.

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Managed to find an £18, 4 ah, 12 volt battery to fit bike, last year I bought one of those 8ah 'alarm' sized ones and it was too big sideways to go in properly, had to sit on, not in, battery box effort.

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Was glad when new floats came but a bit miffed when I found I'd left the earlier arriving new carb gasket at home.

Four now on the road and at least several in bits.

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Mags 1
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May 15, 2019 - 11:22 pm
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My friend Jim today avered that this float is composed of expanded polystyrene, holey I agree, but I'd have thought that too flimsy. All three brass ones are useless, steam comes out of them in the ultrasonic cleaner on full heat.

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Looks fine to me.

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Got both Mzs out today, the 125 actually looks bigger and heavier than the TS 250. The long travel front forks for on/off road use probably have something to do with the height thing I think.

Four now on the road and at least several in bits.

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Mags 1
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May 15, 2019 - 11:28 pm
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It fits nicely and looks the part, I used the 'foot' of my digital vernier gauge to get the 31 I think mm's height I needed.

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I rememberred having a spare new carb gasket stored away for the TS250, so hopefully tried that on.

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No go Joe...much too big.

Four now on the road and at least several in bits.

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Mags 1
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May 15, 2019 - 11:40 pm
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I later had an errand that took me home and I took the opportunity to pick up the correct gasket, which has a triangular cut out for the choke area tube.

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Whilst checking float height and doing adjustement I thought to check all jet settings, I'd bought a new kit and fitted it a few months prior, checking with Haynes I discovered I'd fitted the 120 main jet in place of the 70 choke fitting, reversing these after looking at the packet I still have which I put the old worn jets back into, I read the words to fit MZ ETZ 125/150 (!) How can one main jet be suitable for two different engines 50ccs apart? The 125 should have a 100 jet, according to Mr Haynes.

The last picture shows new carb gasket emptying the (meagre, thankfully) contents of the fuel tank all over the engine, stand and concrete.

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I was hoping to remove the engine and repaint the black upper area one day, once I've got an MOT, I may well be able to sell it on, it's not a bad bike once going, but I've not had it on public roads just yet, a bit early then to be talking about a sale...

Four now on the road and at least several in bits.

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Mags 1
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May 15, 2019 - 11:46 pm
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Various thoughts ran through my mind, could I have overdone the ultrasonic treatment of the carb and caused a porous casting?

As things stood, I deferred judgement and simply put bike away, it's no good tearing out your hair in such situations, I had no other suitable gaskets and I knew gasket goo was no good either.

Tomorrow I could get myself organised and think my way out of the problem, sometimes it pays to not make things worse by attaching blame and trying to effect repairs when you don't actually have the means or acumen at the time to do so.

Four now on the road and at least several in bits.

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cocorico
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May 16, 2019 - 8:11 am
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Some data from my MZ published workshop manual. Main jet 100. Needle jet 70. Float chamber fuel level 12mm (+_1mm). Let me know if you need anything else,

The Bantam Club Forum - all the answers are in there. If not, Google may.

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SpacedMarine
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May 16, 2019 - 3:20 pm
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Mags 1 said

Tomorrow I could get myself organised and think my way out of the problem, sometimes it pays to not make things worse by attaching blame and trying to effect repairs when you don't actually have the means or acumen at the time to do so.  

Know that feeling Mags hence the reason my rebuild has gone quiet 😉

 

I'm sure you'll sort it.

 

James. 

What's 7/16 in mm again?

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Mags 1
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May 16, 2019 - 10:22 pm
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I must say that I'm impressed by folk's positive comments here, I put a request into ebay yesterday for a refund, they wanted me to print off one of their prepaid labels, which would cost me £3.11! Seller's postage I'd paid was 99p...

I cancelled that and sent words and pics of the twisted up gasket and today I was very glad to find an apology and a refund for the whole £3.98 in my account, there are still honest and straight traders on these sites believe it or not.

Four now on the road and at least several in bits.

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Mags 1
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May 18, 2019 - 10:56 pm
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The state of the new gasket after removal the next day.

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Back in the old days you simply got the scissors and hollow punches out.

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Rushed the first one and it was a waste of material.

Four now on the road and at least several in bits.

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Mags 1
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May 18, 2019 - 11:02 pm
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Took my time on the second one, but wasn't very confident, scissors refused to work properly around the sharp bends and I couldn't make my mind which side to hold them, top or bottom, both seemed wrong.

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A fairly recent purchase was this set of hobby type knife blades and holder, about £15 from Aldi or Lidl, usual disclaimers.

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I was glad of the thickness of the thin card material, I felt that anything thinner at times would have been torn.

Four now on the road and at least several in bits.

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Mags 1
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May 18, 2019 - 11:09 pm
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About the eighth time of trying it for fit and I was happy at last, put the three retaining screws in and except for trimming a little excess away on the outside, the new gasket was sealing well all around.

Left fuel tap switched on overnight and there wasn't a dign of dampness today.

Bike is jinxed perhaps, now I've got carb fixed, there's a good strong spark but bike won't fire even, yet another problem to look into now.

It's about this time that folk often wonder about purchasing something a bit more reliable perhaps, like a Honda...?

Four now on the road and at least several in bits.

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Mags 1
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May 29, 2019 - 1:12 pm
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The MZ isn't my favourite bike at the moment, it must be weeks since I've had it bursting into life and ridden it around the private land where it lives, can't seem to get a pop out of it these days. Had the carb to bits six times last Bank holiday Monday, even put the old jets, including the inlet needle jet back in because fuel kept escaping from overflow hole.

I managed to break the new gasket I made, so had to revert to the curled up rubber one.

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I took a compression reading, which went to 90 lbs, not a lot, but enough to start a small 2 stroke I'm sure.

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I then tried a couple of squirts of the oil can down the bore and tried again, an increase of 2.5 lbs wasn't very encouraging, I felt sure it ought to have been more like 120 or something.

Four now on the road and at least several in bits.

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Mags 1
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May 29, 2019 - 1:20 pm
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Every time I removed carb I got a driping leak from the tank supply tubing, even with a screwdriver jammed into it, I decided to cure each fault as I came to it and hoped I'd win through that way. New tap seal is a copy, original had three large hles and one small retaining hole, this one has all four similarly sized. Oil shows up on compression tester at least.

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Had to drain tank to fit it, but I'd only put about a pint in. It does look worn and dirty though.

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I cleaned the sediment bowl out too, or maybe just stirred up the contents a little!

Four now on the road and at least several in bits.

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Mags 1
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May 29, 2019 - 1:38 pm
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The many times used rubber carb gasket was just about finished.

In desperation I inverted carb and tried to blow through inlet pipe, oddly, needle jet wasn't sealing, this was when I changed back to the old needle jet, but there was no difference.

I just couldn't think what to look at next, try grinding the two piece working parts together with brasso etc.?

Put new plastic foats in a bowl of water and noticed that they floated fairly well was a start, suddenly decided to measure width of old and new floats, perhaps new floats were a tad too wide and catching on insides of carb?

Got it, it was only the matter of a couple of mill each side and once I looked I could see vague signs of rubbing on the plastic. I took my B+ D belt sander and took a few mills off each side, hastily assembling carb again for the umpteenth time, I suddenly noticed another 'fault', these floats will fit carbs for anything from the 125s to the 300 version bikes carbs and of course some carbs have slightly thicker pins to hold the floats in, I used long nosed pliers to slightly crush the 'bearings' that sit on the mounting pin, I saw a lot less movement sideways etc after that.

Re-did float levels for third time, in case I'd got the floats out of line with the adjustments etc. at least now carb fills up and doesn't leak any more, a good fat spark from the electronic ignition onto a new NGK plug and one single pop was all I got when I tried the starter.

Plug never gets soaking wet, is one thing I don't understand, I let bore dry out with plug out, no difference. 

I may try pouring some neat fuel in later today.

Something gives me the feeling that an oil seal has packed up, but I hope not, I'm not looking forward to that workload.

On the other hand, I did want to re-paint the engine and spruce it up, to help sell the bike, but an engine strip and painting etc would leave very little chance of any profit margin.

Four now on the road and at least several in bits.

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johnsullivan
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May 29, 2019 - 9:32 pm
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the brass floats can be restored.petrol proof  lacquer works quite well .One pop and dead is sometimes that .. er switch thing that mz put on as a joke.The slide jams too .

67 D10. and a D7    2007 Honda Hornet FA. 93 Yamaha TTR 250 Raid, Sinnis SC 125. 78 Honda 90  75 Montesa Cota 247 an electric scooter of Famous make.

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colk2004
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June 1, 2019 - 9:37 pm
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Keep going, it'll get there...eventually. Got my 1989 ETZ running for the first time last month. It had been abandoned in a back garden over 15 years ago. Been a slow job but worth it. The electrics were a nightmare as the wiring diagram is wrong, the colour codes didn't match on the new wires from Ost2rad. Fix one bit and something else would fail - ended up with help on that one. The carb only having 3 screws in the bowl is still damp on mine but not dripping, and oil piddles out the kickstart shaft which I'll solve soon. But its fun. 

 

Cheers Col

BSA Bantam D10 so so near, Reliant Scimitar GTE SE6a - wiring in bits. FB Falcon 87 seat and wiring to do - still. Ariel Arrow now on the go! MZ125 running, Royal Enfield Classic love it, campervan done to tow some of the above!

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