ETZ 250 Engine Re-build!

[Blurredman]

Hey guys,

So I have finally got around with taking apart my ETZ 250 engine after it seized back in May. All the roller bearings have vanished from inside the conrod bearing! One is fused to the conrod itself! Fun huh!


I'm going to replace all the bearings obviously because there is a hell of a lot of metal fragments and debree in the crank chamber.

Can someone supply a list of all bearings that are used? What's people's experience.. Am I best go to straight to Japanese.. And what about those huge crank ball bearings? Who on earth supplies those !?

For example.. This looks pretty good! It's got all I need and at what I perceive to be a fair price other than a small end bearing... https://www.ebay.co.uk/itm/MZ-ETZ-250-2 ... Sw4DJYmIM5

Thanks

[JohnP]

Try Burwins in Essex 07726000075, all you want will be in stock and plenty of advice too...John

[ivor]

I have used https://www.ost2rad.com in the past.Very good, you can search the parts section by section and put parts together into an order. Postage and prices are keen, though not as good as before the falling of the pound. They send the order through very quickly. I have been very pleased with them. Bearings/seals etc usually available as a kit.
On the other hand you might want to ring up a British supplier if you want to ask questions.

[Blurredman]

Ost2rad seemed to have a pretty good deal on the whole bearing kit so I went with them.

Either way, i'm not sure what kind of quality control the DDR bearings went through, but they lasted well. I'm only replacing because the engine is open and I may as well do a full run-down. The bearings feel pretty good, even after almost 30k miles and the big end letting go. Plus I've never taken an MZ apart other than the barrel and clutch side casin before. Never needed to.

I look forward to putting the enging together, and don't imagine it will take that long. Only took a few hours to strip it down to nothing, and part of that is down to seized flat head screws. I'm also quite interested to note how there is no gasket between crankcases, but just a sealing compound.

There is only one thing I may have continued problems with and that is removing a single gearbox bearing that cannot be punched out from the opposit side.


Anyway.. Once this is done. I'll have to explore the clutch on my daily 251 and see if the plates have excessive wear. They feel like they might be quite worn now. When I last had the casing off, I noticed the clutch had been improperly put together.

[ivor]

Have you tried heating the case in the oven before attempting to remove the bearing ?

[Blurredman]

I haven't tried removing any bearings yet.

But according to the over-haul video on youtube, the bearing requires a puller that expands behind the inside race.

From 12:25 minutes in..... https://www.youtube.com/watch?v=4J70JChZ9e4&t=3439s

[ivor]

You could try heating in the oven, then turning the case face down on a plank of wood and banging down sharply, the bearing may then drop out. Or find someone with a lathe to machine a mandrel out of aluminium or steel to just a thou or two under the inside diameter so it's a close sliding fit. Then two thirds fill the hole with thick oil, put the mandrel in the hole, hit with a hammer and the hydraulic pressure should push it straight out. There are videos on Youtube showing it being done I think.

[Blurredman]

Well I got all bearings out other than the one I specified.. Even the crank bearings were alright! I will think of some plan to remove it somehow.

[ivor]

The hydraulic method is a very good way.

[AlanJ]

Hi Ivor,
Please excuse me asking, but wont the oil under pressure go round the corner and then through the ball race? Or am I not seeing this right? Incidently you can get an internal bearing puller from Ebay for a tenner, but not sure if there is enough room under the inner race for the jaws to hold and at that price it will be from China so, who knows. Just had a look on Ebay and the puller is £14.69
Take care Alan.

[ivor]

I thought we were talking about a bearing in a blind hole, if not then sorry. I'm not familiar with the 250, the TS125 internals are another matter !
A puller meant especially for the job at that price is worth buying.
Or perhaps an expanding bolt meant as a heavy duty fixing in building work could do. If the bolt was a common thread get a longer bolt and slide something like say a socket over the shaft and use it as a slide hammer.

[Blurredman]

I believe there is a little space behind the bearing but not much. Just enough to get a bearing puller in. I hope I can borrow one off my neighbour as this is one of the only 'special tools for vehicles' that I haven't bought over the years. The bearing itself is open sided and is a 6203, so internal diameter is 17mm according to specifications on the internet.

[Skyeport]

The space behind the bearing is quite small. I bought a bearing puller from the local tool supplier, but there wasn't enough room for the jaws, I'm sure I'll use the puller somewhere else...maybe.
Be cautious with the hydraulic method, there is only a thin bit of alloy behind the bearing & too much pressure on a stubborn bearing may pop the case behind the bearing, don't ask how I know, although this makes it easy to get at the bearing from the other side..................

[AlanJ]

Hi Guys,
I know I am a thick old bugger, but will somebody explain how the hydraulic system works because I can see it might move the bearing a little, but as soon as the bearing moves then the oil can go under the inner race and then through the ball race so it probably wont work after the bearing has moved a small amount. If the inner race is smaller than the outer, then the oil will go round and probably not move the bearing at all. Guys come on and tell me I am not seeing this right, I don't want to offend anybody, just understand. The reason I am asking this is after I have finished the refurb on my Honda CB400A, I will sort out the Saxon in the boxes so, there is the 301 for that and I have a spare 251 so there I is a good chance I might have this bearing problem, so.
Take care all Alan.

[Skyeport]

I am not sure how oil would work either?
I used candle wax not oil, same principal just thicker & doesn't leak through the bearings as easily.