Faltering ETZ 250

[Andy_C]

My ETZ has started doing something rather odd.

Starts fine, runs fine for about 10 miles or so, the first thing that then happens is if you leave it ticking over it will all of a sudden stop as if you had switched the ignition off and emits a little "pop" from the silencer, sometimes after it does it, it will start easily, other times not.

The other thing it does is when you close the throttle, the motor will not always pick up again, and if it does you have to have it at nearly full throttle for it to pick up, it only starts doing this when you have done 10 miles or so and the engine is really hot - its almost like fuel starvation.

Bit lost for ideas, checked the carb, battery is in good condition, iridium plug, timing as it should be.

Wondering if perhaps it is the timing side crank seal, as I am sure that there is a whiff of petrol when I take the cover off, if not that then possibly the coil breaking down - recent new capacitor - not the problem as it used to do it with the old one. Cant be the primary side oil seal as there are no signs of smoke from the exhaust other than 2T smoke.

Its a real shame as this bike has ran really well in the past.

Any thoughts ?

[DAVID THOMPSON]

check the wire spades one of them may have lost its tension with age
my travller had the coil wire just fall off one day and i was thinking
what now and looked down to see the spade had fell off the coil plus side
when i hit a chuck hole in the road
lucky me i did not have to push it home
dave

[Blurredman]

Coil.. ?

Mine used to do similar.. very sudden 'turn off ignition' type engine shut down, with a little pop/puff from the back as it backfired.
Sometimes I could re-start (only after 3 kicks exactly, no less) and make it a little bit further between stalls. But sometimes I was stuck for a good 5 minutes before I could carry on.


Coincidentally, my brother's original coil also went the way of the dodo.



Try swapping it out for a while and see what happens.

[Puffs]

Yes, it does sound like an ignition problem to me too. When it stalls & does not start again, do you have a spark?

I've had another bike with similar issues. But after a while that died on me completely, which makes it easier to diagnose - and there it was the coil.

But it can also be a loose connection somewhere (or maybe even a cable in which the conducting core has broken due to vibrations), that's harder to find.

[Andy_C]

Swopped out the coil for one that I have on the shelf - 12V but not MZ.

Hoping to give it a test run tomorrow.

I'll report back..........

[Andy_C]

Took it out for an early morning thrash this morning - quiet roads cool morning air.

Please to say that it showed any signs of faltering / mis firing, in fact dare I say it has never gone so well.

I shall consign the old coil to the bin once I am 100% sure that the problem has gone away.

Many thanks for the advice.

[Andy_C]

Now that normaility has been restored, it crossed my mind that it would be sensible to re locate the coil. away from under the seat as there is little air flow in that area so in all probability the coil will fail again.

I dont see any place that it can be realistically re located where it will get some air flow due to the size of the coil, so I was wondering whether anyone here has used any smaller coils reliably, and if so what is the part number / manufacturer of the coil.

Seem to be quite a few on ebay, but which one to choose?

Probably end up welding a bracket to the frame under the tank.

Any thoughts ?

[Blurredman]

I wouldn't buy the coils that are listed specifically for MZ 250's. I had one once and sent it back. Coil worked fine cold, but gave problems when warm..

And yeah- I hear you concerning places to put things on the ETZ. I hate the lack of space under the seat..

[Andy_C]

Blurredman.

I'll just have a poke around the web to see what coils I can find that would fit under the tank.

Mind you if it was the original coil on the bike it has done pretty well, so I wonder if it worthwhile moving it.

[Blurredman]

That's what I thought when mine broke and my brother's broke.


Mine is an 1990 and was at 29k before I had it. Obviously one of the reasons it had been abandoned was the stalling issue- But perhaps not, and that 13 years standing was just not good for the coil?


My brother' s ETZ250 is an '85 and that only recently went, it has only 20k on it.

My '87 ETZ250 has 30k on it now and still has the original coil...

There's no pattern really. They don't even list resistences in the official manuals, stating that only MZ technicians can determine whether it is at fault or not.

If it takes 30 years for your new one to break again.. That ain't bad..

[Puffs]

If a coil fails after 30y, maybe it's vibration or internal corrosion? If the issue were temperature @ that location, that would be a design flaw, but then I would expect failure to come much earlier. Remember that these bikes had, even when they were young, some 50+ years of design experience behind them.