MZ/MuZ Riders

Hello,

I have Bing 84 on my ETZ 251 purchased from ost2rad.com. This is my problem: the power of the engine is quite low at begining (about 1500rpm) so it is problem to drive off in the hill for example (I must use clutch tooo much). After that in the middle RPM it have good draw I think. But at the higher RPM, lets say about 4800, it starts to be weak. For example at 4. transmission grade it can't achieve more then 5000RPM on the horizontal road }which means less then 90km/h). On 5. transmission grade it doesn't accelarating more then 4300rpm (again 90km/h), then veeery slowly, maximally to 4800rpm. Lets say my maximally speed is 90km/h and thats too low.

I have gear with 20 sprockets.

Can you help?

it may be geared too tall

and exhaust pipes other than stock can cause lots of problems

dave

How do you mean - too tall - I have written there is secondary gear with 20 sprockets (21 sprockets is on original Mz).

What do you mean by stock exhaust? Do you mean original exhaust made in Germany (not available yet) or just original exhaust? If so there is original new exhaust made in Hungary although for MZ ETZ 250 - it may be same as for 251 just a little bit longer.

Your gearing is ok,
what exhaust do you have fitted is it clean internaly, they can get full of oily sludge and hard burnt on carbon , is the exhaust port full of hard carbon . The exhaust plays a major part in making power if its a bit blocked up you get the symptoms you have listed.
Etz s have little or no power below 3000 rpm and it tails off at 6000 rpm so its normal to use some revs and clutch slip to get going on a hill.
If the needle in the carb is on a high clip setting its a bit weak and will need lots of revs to get going, if its to rich it will pull well at low / middle revs and get wooly and refuse to rev out.

Try this
Make dam sure the air filter is clean with no blockages

Confirm that the fuel tap/pipe is flowing freely

clean the exhaust take it off. block one end and fill it with a strong mixture of caustic soda and leave overnight to disolve the carbon.give it a good rinse out with water

check the exhaust port for carbon deposits

Set the carb up for YOUR BIKE !!!! that carb can be fitted to a number of two strokes and they will all have different jet sizes and needles, needle positions.

Is the bore piston rings worn out

Make dam sure the air filter is clean with no blockages
-DONE, filter is new and clean

Confirm that the fuel tap/pipe is flowing freely
-DONE, fuel if flowing absolutellly freely

clean the exhaust take it off. block one end and fill it with a strong mixture of caustic soda and leave overnight to disolve the carbon.give it a good rinse out with water
-DONE, exhaust burned with gas and then cleaned with NaOH

check the exhaust port for carbon deposits
-DONE, no carbon there

Set the carb up for YOUR BIKE !!!! that carb can be fitted to a number of two strokes and they will all have different jet sizes and needles, needle positions.
-DONE, carb us setted up in the best way

Is the bore piston rings worn out
-DONE, piston rings are new couse I have engine 5000km after General Repair.


However all problems persist.

However all problems persist.

this means the ignition system if probable screwed up

just my experience with old BMW magneto fired bikes

6 volt point and coil systems suck and 12 volt ones are not much better

dave

these things are just big mopeds 250 cc is good for 55 mph over that is pushing it to hard for it to last very long

DAVID THOMPSON wrote:these things are just big mopeds 250 cc is good for 55 mph over that is pushing it to hard for it to last very long

Rubbish! I ran TS250/1s for many years. They were happy at 70mph day in day out. Top speed of an ETZ 251 is a shade under 90mph.

Come across quite a few stories of problems with the Bings being sold these days. I think they are being made in China these days and the quality control seems iffy to say the least.

i am used to the jap 2 smokers from the 1970's

and a 250cc at 70 mph was usually a hole in the piston in short order

the ones with auto oilers would do better than most
but till the water cooled units came out they were not very good
i knew about MZ but there never seemed to be any one selling them
till the 4 strokes arrived
dave

Hi
Is that the cheap version og their Bing Carburetor you have choosen ( Chinese Copy )or the Expensive version
the chinese copies dont run very good , most of them dont run at all

Hi!

Why would that be? I mean, why would a bike not run, or run poorly, with a Chinese carb, after you have properly adjusted it (jets, cut-out, needle & guide)?

Carburettors are pretty simple, but you do have to adjust them properly.

DAVID THOMPSON wrote:i am used to the jap 2 smokers from the 1970's

and a 250cc at 70 mph was usually a hole in the piston in short order

the ones with auto oilers would do better than most
but till the water cooled units came out they were not very good
i knew about MZ but there never seemed to be any one selling them
till the 4 strokes arrived
dave

I rode,service,repaired, raced, tweaked and obsessed on 2 stroke, singles,twins and triples for years up to a year or two before water cooling became de rigueur and saw a few nip ups (fixed with honing) but rarely a hole in the piston. Full on seizures were usually explained by lack of lubrication rather than overheating. I'm not arguing simply comparing my own experience.

I too, had heard of MZ's but they we're considered to be "communist crap" by the Japanese two stroke biased auto trade community that I grew up in. Unfortunately the MZ's were tarred with the same brush as M series Urals that arrived in the early to mid '70's.

I just realized the original post was 3 years ago.
@JurassMZ has probably sold his 251 and bought a Grom by now

GROM = little town bike by Honda selling really well in the usa to replace all the honda trail 70's that are worn out

Puffs wrote:
Prejudice is why I reacted to the comment on the Chinese carbs. My experience with those is limited to just 1, but that has worked fine (for more than 30 000 km by now). It's just that if you buy a carburettor off the shelf, any make, you have to adjust it to the bike you fit it to. The manufacturer doesn't know beforehand what bike it'll be fitted it on, and the generic jetting he put in may not work for your bike.

Very true.
A replacement carburettor for a 70's vespa, came with jets which were far too small and it ran awfully. Put in it the jets from the original carb and the user can make full use of the engine/carburettor characteristics!