MZ/MuZ Riders

Hiya guys.

So my wreck of a 1990 ETZ 251 now seems to be coming together fully and proving to be much more reliable and running on point too now that it is running electronic ignition but it definitely has a lack of power compared with both my other ETZ's..Which feel much more spritely.

It is a bit lacklustre to pull off from a standstill, but seems fine up until 4k. However getting beyond 4k is a bit of a struggle. It will rev to 5.5k but it is quite laboured and slow, it definitely does not produce the powerband that is so well known in that 4.5-5.5k region. It is the opposit actually to the reason that there is no point in reving it beyond 4k as it produces nothing but a gradual but very noticable decline in power.

The bike:

New electronic ignition and timed correctly,
I've changed the coil for a known working one,
Regulator is solid state.


What else could be causing this lack of power? It feels much more like a 125 powerwise.

Blocked exhaust ?

Have you tried cleaning it out with Caustic Soda ?

Thanks for getting back to me. It's an interesting point.

The exhaust has 30k on it now.


I assumed that the power was electrical though really it gives the indication of not being so.. Never assume.


I've never actually cleaned out a 2t exhaust however, I very much know the technique. How much caustic soda is required? (Where do I get it from too), and how long should I wait to concede in emptying it out and re-installing it?

You can get Caustis Soda from "old fashioned" hardware shops - no chance of getting it from a supermarket !!

I get mine in 500 gramme containers its normally used to clean drains and works really well.

Strength - good question, I normally use about 250g with enough water to fill the silencer - mixing info is on the container anyway.

You need to plug one end of the pipe and pour the solution in the other end and leave overnight. Then drain out the gunge and re fit to the bike and run it ASAP to dry out the pipe.

If you do use this method treat the caustic with respect as it is very alkaline and WILL remove skin - rubber gloves are essential and pour the gunge down the drain.

The other alternative to getitng teh carbon out of the pipe is to set it on fire with an oxy acetelyne torch (you can find this on the web) downside of this is that it will colour the silencer blue with the heat and it produces lots of smoke but it is far more effective than the Caustic approach.

Both methods can be found on the web.

Gotta be worth a try.

Is there any way you can check the compression
to check the health of the engine?

Regards,
M

Hiya guys,

I've yet to have time to do this. On the weekend I was working on my CX500. Notibly, taking the spare engine out, swapping some components with the original engine I've been rebuilding, then buttoning up the spare engine and putting it aside for the future, then putting the original engine back in.... Was a long and tiring day with the bad back I already had


Anyway, Friday night (from 2:30-5:30 am) I went for a ride on the MZ in question on this topic. It ran fine thanks to the new electronic ignition, but I did some experimentation. For example, on some long straights I pulled the throttle back to get the rpm to 4.5 and I pulled the choke. Doing this allowed the engine to get past up to the 5.5k region... I am thinking to myself now if I need to look at the carburettor now. I am at work, but lunch time I will pull the main needle up one notch and see how the bike performs on the way home form work.


As for bike compression, I know the bike has had a very hard life, the original piston was seized solid in the barrel for rust. I had to batter the piston out so hard I am suprised I didn't hole the piston (was using a very large socket and there are indented rings all around the piston). Never-the-less the piston is very scored anyway, obviously the bike has run dry of 2t oil many times and has also been involved in heat seizure too (a different seizure type to oil deprivation seize).

I'm currently running with a spare barrel/piston/head that came off an ETZ of mine where I put on a 300cc piston, so there's no issue with compression. I also put new piston rings on it when I installed it 600 miles ago, there shouldn't be any problem there.

Does the fact that pulling the choke allow it to rev higher a fuelling issue or is that just a mask 'resolution' to a fake problem that I will end up chasing falsely? I'm intrigued. It is pretty gutless when going up hills, and doesn't tend to smoke all that much which leads me into thinking it might be running lean. It starts first kick recently, and I've always said that an MZ that starts first kick is not one that is properly set up.

Well changing the needle position didn't work

Okay guys, just to update you on this.


I tried a little experiement. Before I went to work today I put the needle in the middle position, rather than the 4th (from top) I always use. The 4th position is what I find makes an ETZ250 run the best all around on both my other ones. But those are N2.5 carbruettors. The needle in the 5th position was just way too rich, and the needle in the 4th position as I have been experiencing is a little too rich too for the higher RPM. The needle in the middle position allows it to rev out fully!!

Of course, I have less power lower down so I have to use my gears a bit more, (this motor is quite gutless anyway), but I definitely get that kick of a powerband when I reach 4.5k now and it revs to at least 5.5k (no point going more than that eh?).


Some point soon in the future I will clear out the exhaust, but essentially it doesn't seem so much of an issue now. Not the cause of this problem anyway.


Thanks guys for the help!

Glad to hear that things have improved.

My ETZ quite hapilly revs right out without any hesitation and pulls pretty cleanly.

Needle is in the mid position.

clean exhaust may help... and i have noticed several complaints over the years that some after market
pipes can be trouble as there not very good copies of originals
dave

Original pipe.

Interestingly, the only reason I have this bike is because I was looking for parts, namely the pipe and the carburettor...

However, I decided it would be worth putting on the road with a little work... So far the bike has only cost me:

£100 for bike
£100 for bits and bobs and electronic ignition
£40 tax
£21 MOT (I get it on trade)
£30 to change over insurance from my other MZ..


Though I had to: use a spare barrel and piston, and HAD to install electronic ignition.


£291 total to £310 for everything all in.. Not bad really. Though it looks like a piece of rubbish, but it spends all day and night outside and is my commuter.

Some things wrong with it: Somehow the previous owner/s have smashed the return stop for the kickstart.. There's no way I could even use a proper rubber stop because there is no fitting for it anymore If I don't pull it back it engages with the gear slightly. I have selotaped a bottle cork as a stop on the lever for now whilst I can find a proper resolution..

Does anyone have a spare clutch side cover??? My purpose is to keep this bike running for as cheaply as possible, but I don't want it wrecked as a result! The more MZ's on the road, the better. I would gladly ride to you, and buy and fit there and then if you provide some cups of tea!!