250 clutch springs

[Blurredman]

Been chasing this issue when I first got the bike years ago - occasional clutch slip!

I used 20w50 as I found that was best for reducing slip.


Then I decided to remove the clutch to check the plates. Big mistake! I found the taper on the crank and clutch to be totally messed up, and no matter how much it was torqued it came off.
I had already bought some more expensive 'Hungarian' springs at euro 1.50 each and i also bought a set of RAM indian springs at 50c each. So I installed the hungarian springs and then got the clutch welded onto the crank. Knowing that at a later date it was to be rebuilt (but I didn't have the money or opportunity at that time).


So a year or two later I did rebuild the engine completely:
viewtopic.php?f=20&t=9593

I had sourced a used but complete clutch unit with a lovely taper to fit onto the reconned crank which I had brought back on a holiday.

I did take the clutch apart but I didn't check the 'spring length'. Plates were fine though. So all was installed and since the rebuild I had still got my clutch slip problems on this particular bike.
The other day I took the clutch off and measured everything including the plates and the springs that came out (which I think were original but of course quite undatable- I had no idea where the clutch came from- anything from 1979-1997 I guess) - Plates were good but I measured a difference of 2mm I think from the longest and shortest spring. I put the cheap RAM Indian springs in which although measured 1.5mm smaller than the manual stated standard, they did feel tougher and they were all consistent.

The clutch slip was still there- potentially worse. So I still had the crank and clutch unit that I took out of the machine when I re-built it, and took the 'hungarian' springs. They were although at the lower end of manual stated spring length, they were consistent and all 1.5mm longer than the Indian RAMs. I installed them.

The clutch lever is you can tell a lot tougher- and I went to test on a specific hill that gives both high speed run up with an increasingly sharper gradient and I do not THINK I had clutch slip. It used to be quite obvious- 4-5k, it might jump from 4k-4300rpm in a half second and catch and continue to grab. But.. I don't 'THINK' I felt clutch slip today with these Hungarian springs. Certainly didn't jump 300rpm..

Using 10w40 MA2 Semi Synth. I think the oil might be too slick, and I will make a note not to use 10w40 on the machine come next oil change, but stick to my 20w50 or get gear oil. This should remove all doubt.


Moral: RAM may be cheap- but is cheap for a reason. Think about what type of requirement the item fulfills. If it's something innocuous then fine. My RAM pistons are still holding up- But I honestly don't know how much longer they'll last.

[Blurredman]

I also forgot to say. For anyone that was interested- this is the inside of the 'internal oil galley'.

You can see in this image below where the 'join' would be:

[nice2day]

Hi Blurredman...makes me wonder if the clutch pressure release centre is fully moving off the clutch ...You might have cable slack but is the pressure release hub adjusted right as it might be in constant contact?...Just a thought as you would be unaware it was spinning the centre bearing around continuously.

Bet you say "of course it is !!!!' .... but worth a guess I reckon...Good luck...

Les

[Blurredman]

The clutch is smooth in operation and just slipped at 'powerband' range.

Anyway. Ride home was unsuccessful.. time to try a different oil.

[DAVID THOMPSON]

i had a bike once that the lever was not pulling a full stroke

if it did not slip at high speed it was hell getting it in neutral
unless you got neutral before a complete stop
it had a bent alloy handle bar lever

Dave

[Blurredman]

It is interesting. I suppose I know everything in the clutch is 'good' in terms of specs.

I've never actually used 10w40 before. The stuff I removed was Motorcycle compatable (semi synth too). So I've now got some 20w50 (mineral) in it- the clutch is zip tied closed at the minute. Will take it for a ride tonight and update!

I only used to put 20w50 in this particular machine. But we'll see what happens. If it still slips after some test rides I'll start looking into the SAE 80 transmission oils out there


I really wish I knew what I put in my other MZ- I have the feeling I put 10w40 in it, and clutch operation on that is perfect

[Puffs]

Following a biased and flawed moderator choice (someone posting aggressive personal attacks is rewarded, while my technical posts are removed - behind my back & without any justification!), I have withdrawn from this forum.

[Blurredman]

I agree with you there Puffs and would like to know what everybody uses.

After years of varying results with various products, I noted this in the official service manual:

"In countries other than the GDR, engine oil SAE 30 or 40 or gear oil SAE 80 with similar properties should be used." (as opposed to "GL 60").

I used to get a different symptom of problems with each different gear oil I happened to buy. They'd all be 80w90 GL4, but they all felt different - For example the 'Comma' stuff pretty much had the clutch locked up until some warmth was in it which wasn't a nice experience. And other oils had slip problems too.

So I found the above comment and didn't have a problem again on my ETZ 250/300. The 251 is a different machine which has different tastes it seems


Anyway- I couldn't really justify spending £10 per litre of transmission oil just to 'try out' esspecially when you can get a galon for £19 which would be a waste if it didn't work.. If the manufacturers sold the oils at £4 or even £5 for 1l bottle i'd go for it but I didn't and I settled on the motor oil- because I always have plenty of that.


As it happens- I didn't get the opportunity yesterday- but I will come back with my results. If it still fails I will be buying this stuff:
https://www.ebay.co.uk/itm/Hypoid-Gear- ... 0290.m3507

I can at least slowly (very) use it up in the rear differential of my Honda if it doesn't work on the 251.


I presume that clutch material has never been changed throughout the 250/251 lifetime.

[Puffs]

Following a biased and flawed moderator choice (someone posting aggressive personal attacks is rewarded, while my technical posts are removed - behind my back & without any justification!), I have withdrawn from this forum.

[Blurredman]

Ah yes. Where did you get that manual from? I have never found one specifically for a 251, in German or otherwise..

I was using the English 1981 ETZ 250 official service manual - as found in my FTP.
I notice your german lists "gl100", as opposed to the 'gl60' the 250 has recommended.

Anyway. Other than the replacement springs (which are a lot tougher to pull than my other bike with original springs and no clutch slip), the clutch as a whole and all components all look original manufactured. It's a nice day to-day.. I'll go out and give it a test. It's been raining 3 days straight until now.

[Guesi]

But what MZ does NOT say that you can use multigrade eninge oil.
They recommend 30 or 40 unalloyed oil.

And multigrade oil is something completely different...

It is for eninges and NOT for gearboxes. Many additives of these oils are contraproductive for the MZ gearbox and especially the clutch...

[Blurredman]

Indeed- I will try an EP80 oil next time for both MZ's. The problem is.. most automotive places only do multigrade- which can give problems.

But for now- I went for my ride and all was successful.. no slippage. No slippage on the hills, and on the 'hoon' back on the dual carriageways between roundabouts- no slippage.

At least I know I have a safe base now that I can go back on if I have issues with other oils in the future. I will mark down for my own records what I have used- and what did or did not work - And indeed what I Intend to use come next oil change.



And yes- I am aware of how I sound, complaining about something when i'm using the 'wrong' stuff.
It's not complain- but more a personal insight for this issue and information for those in the future.

[dave47]

Hi blurredman,
I've also used Comma EP80W90 from Wilko's for several years only because it seems to be the cheapest local to me,and I've never had any problems with the clutch slipping or sticking in the ETZ250. So I think it is probably your clutch components rather than the oil that is the problem. I do free the plates before switching on the ignition.

[Blurredman]

Hi blurredman,
I've also used Comma EP80W90 from Wilko's for several years only because it seems to be the cheapest local to me,and I've never had any problems with the clutch slipping or sticking in the ETZ250. So I think it is probably your clutch components rather than the oil that is the problem. I do free the plates before switching on the ignition.

Hi Dave. Thanks for your interesting input! Maybe there are clutch plate differences.. I actually bought a few litres at the time (years back when I tried them) because for £4 per litre bottle it was a good way to both a) get the oil and b) get it in the bike without spilling..
And with both bikes I found the clutch seemed to be dragging through the gear changes until a few miles into the ride. That was my experience.
That was Mineral- maybe you used semi-syth or you use mineral as well?

All I know is- esspecially with my '87 ETZ 250, the gear changes are the smoothest I've ever felt, and clutch behaving as it should- with 20w50. With my 251- the gearbox is rather more clunky, which is why I decided to try 10w40, only for the clutch to slip.

Anyway. Thanks

[Puffs]

Following a biased and flawed moderator choice (someone posting aggressive personal attacks is rewarded, while my technical posts are removed - behind my back & without any justification!), I have withdrawn from this forum.