MZ/MuZ Riders

Hi All,

I've reluctantly come to the conclusion that 30 years of sitting idle have rogered my 1977 TS125's crank seals, and that they're the cause of it's failure to run.

My Haynes manual has gone walkies so can anyone tell me if the crankcases have to be split in order to change the seals?

TIA, Richard

I don't see how. The crank seals are behind the main bearings.

Hi,

Here is the official service manual.


It does look like that the main seals are on the crank side of the bearing, and not the outter side. Which does mean splitting. I've never actually touched a ts125/150 so i've no personal experience, but that's what it looks like from the manual.


I'm actually going through the same process (albeit on an es250). Upon opening my engine, the seals do seem rigid and brittle and there are cracks. It is said to be a common thing with 2t's that when unused the seals degrade more than they would if the bike was in use.

You can be lucky (I was with my 13 years unused ETZ251), but also unlucky, with my ES250. My symptoms were an overly HOT engine (for the little time it was actually running), unable to idle, excessive choke needed.

I feared as much ....!

Back in the '80s I bought two ETZ125s and one ETZ250 (not all at the same time), each had stood idle for a couple of years and on both 125s I had to change the crank seals. I can't remember splitting the cases - but my memory's not what it was.

I've now read through the official manual & I'm slightly worried by the number of special tools. Does anyone know if they're all needed? Or available for hire? The mandrel for heating the bearing inner looks like it might be essential!

Many thanks to All
Richard

Hi Richard,
Although the manuals show a few special tools (f you have them, then great) but other than a clutch puller, most of the bearings and seals
can be replaced with the well-known system of heat and cold. You just have to improvise, ie a seal usually goes into a casing, so, heat the casing freeze
the seal. Most of the time it works. Anyway wish you well, Alan.

Hi again Rihard,
I forgot the mandrel bit. Most people have a soldering iron or the right size heated socket.
Stay safe Alan.

Hi, I have just completed a full rebuild of an ES150 which is practically the same as the TS which is in turn a bored out TS125.

In answer to your question, yes you have to split the casings as the crank seals are on the inside. Regarding tools you will need a puller to remove the primary drive, mine was the duplex twin chain one so I had to make one up, as a standard two or three leg puller will not fit behind the sprocket. You will also need a clutch holding tool again easy to make with an old clutch part.

Splitting the cases was simple enough, for me the biggest headache was getting the gearbox set up again and the ratios all within spec during the rebuild. Whilst you are in there for all it costs you are better to replace all the bearings, gearbox and crank, six in total as well as the crank and all other seals.

As mentioned; the old fashioned method of putting the casings in the oven and bearings and crank in the fridge still works no bother just follow the steps in the original manual if you have one.

Strangely enough I’ve just done a 1978 Ts150 without splitting any cases. There must be a cut off point on these where very early ones need splitting and later don’t. So all I can say it must be just before mine as it’s a 1978 bike.

I doubt if the basic design changed much from c1939 to c1985. RIP Hermann Weber. The seals were on the inside until the ETZ125/150 in c1985, so its either split the case or pull out the bearings.

If there's anything I know about owning a few varients and researching MZ's over the years, MZ's DO CHANGE.

The thing is, they change so subtly and gradually that it might be forgiven that things are interchangable, and this goes for Engine stuff as well as anything frame related. Just look at the differences between the ETZ250 and the ETZ251! Some things are quite different! Other things are slightly changed but may still work.