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MZ Buggeration

Posted by Andy C <iframe src='https://members5.boardhost.com/classicbikemart/info/user=Andy+C' width='330' height='300' border=0 style='border:none;'> on April 10, 2022, 9:26 am

This bike is really pushing it's luck.

I was starting to get used to riding it, and actully quite enjoying it, however yesterday as I was literally a 100 yards or so from home the clutch started slipping, and by the time I reached my drive, I had no drive to the rear wheel at all.

Anyone who knows these bikes knows that the clutch is held onto the crank via a taper, and the clutch centre nut being tightened up correctly keeps it held on the taper.

Well mine let go of the taper despite the nut being done up correctly and everything being degreased prior to assembly.

Pulling it apart, the taper on the crank has just a few marks on it, but the taper in the clutch hub is beyond replair - guess it is softer material than the crank.

The handbook recommends that if you have issues in this area then you can use a little fine grinding paste to remove any surface imperfections, or some very fine emery.

No problem with doing that, but I cant see why it hapenned in the first place as the crank and clutch tapers looked in good shape when I put it together, and I tigtened the centre nut correctly.

Guess I'll have to check / double check when I re assemble with a new clutch hub.

Damn it........

Who needs a signature anyway......

Re: MZ Buggeration

Posted by Nigel B <iframe src='https://members5.boardhost.com/classicbikemart/info/user=Nigel+B' width='330' height='300' border=0 style='border:none;'> on April 10, 2022, 11:08 am, in reply to "MZ Buggeration"

Been there - had that happen.

How did you lock the crank to do the nut up ?

I found (the hard way) that the only safe way is to raise the barrel & put a hardwood spacer under the piston to do the crank end nut up to the specified torque (around 100NM - see manual). I initially made the mistake of doing mine up in top gear with the back brake on until the clutch slipped, as I didn't have a torque wrench at the time. After the clutch came off (like yours, but several miles from home) I did some checks with a torque wrench (after I bought one ! ) & found that the clutch slips at around half the rated nut tightness. I was not comfortable with the other recommendation of stuffing rope down the plug hole to block the piston - IMO this puts too much load on the piston skirt. Blocking the piston under the skirt as recommended by the factory (there is a drawing for the tool to do this in the manual) puts a compression load on the skirt, not sideways.

I made a dummy bearing to act as a spacer to do the nut up without the clutch cover in place & warmed the brake cleaner degreased clutch centre to just bearably hot with a hot air gun ( a recommendation that came form MZ Rider IIRC) before putting it on the brake cleaner degreased crankshaft & doing the nut up to the rated torque. Let the clutch cool, then remove the nut & spacer & refit the cover with the nut done up to the rated torque again.

The dummy bearing is required to prevent damage to the tacho drive gear that is part of the nut (you know how I know this ! ). Bin the damaged clutch drive plate - you won't satisfactorily repair it so that it drives properly & you run the risk of removing the axial clearance on the drive gear that runs on the crankshaft so the clutch won't disengage if lapping it with grinding paste.

If your engine has been apart before you got the bike, the clutch centre may have had historical damage.

This is an area that, if done correctly, works well - but is very intolerant of any shortcomings in parts or assembly method.

Keep at it - you will get there eventually !

Nigel B.

Re: MZ Buggeration

Posted by Andy C <iframe src='https://members5.boardhost.com/classicbikemart/info/user=Andy+C' width='330' height='300' border=0 style='border:none;'> on April 10, 2022, 11:53 am, in reply to "Re: MZ Buggeration"

Thanks for the tips Nigel - managed to find a new clutch centre and is now on order.

I am going to see if I can dress the crank taper with some very fine emery before attempting re assembly.

Must admit that I locked it previousley using the top gear method as you did - so a lesson learned.

Thanks for the tips re the heat gun - as I did the clutch on my ETZ I am familiar with the spacers etc, the ETZ never gave any problems.

Who needs a signature anyway......

Re: MZ Buggeration

Posted by geoff the bonnie <iframe src='https://members5.boardhost.com/classicbikemart/info/user=geoff+the+bonnie' width='330' height='300' border=0 style='border:none;'> on April 10, 2022, 1:04 pm, in reply to "Re: MZ Buggeration"

How would Wernher von Braun have fitted it ? I bet it would have stayed on if he invented it.

Re: MZ Buggeration

How would Wernher von Braun have fitted it ?

Von Braun had nothing to do with MZs, so why would his opinion have had any validity ?

After all, MZs are not Rocket Science !

Nigel B.

Re: MZ Buggeration

Sure you dont mean Walter Kaaden? - there again he was more of an exhaust man.

Think the failure may have been part down to me and the method I used to tighten the nut and possibly it had been previousley damaged.

Anyway, hoefully all will be well when the new hub is fitted, and correctly torqued.

Who needs a signature anyway......

Re: MZ Buggeration

Its a joke. Braun did some very good engineering back in WW2 and for the American space projects. Most of it stayed together except the V1 and V2 which were intended to break

Re: MZ Buggeration

Braun did some very good engineering back in WW2 and for the American space projects.

Not sure about that. The quote below is from a Smithsonian interview * withg the author of a book about Von Braun :

I mean he was incredibly talented. His real talent was not being a scientist or an engineer. He had a Ph.D. in physics, but he really was an engineer. But it was engineering management: He had this talent for managing large engineering organizations. Not only managing but also constructing these systems for building really exotic new technologies. And he had a vision of how to construct this giant engineering team to do something that no one had ever done before. And that was his real genius. In terms of nuts and bolts invention of technology, he wasn’t any smarter than a lot of people. And probably wasn’t even as good as a lot of other people. But as an engineering manager, he had a very rare talent.

So more of a manager with a vision rather than hands-on engineer. And he had nothing to do with the V1, which was a Fiesler aircrft / Argus engines development.

Nigel B.

* https://www.smithsonianmag.com/air-space-magazine/a-amp-s-interview-michael-j-neufeld-23236520/

Re: MZ Buggeration

Posted by Tonupdave <iframe src='https://members5.boardhost.com/classicbikemart/info/user=Tonupdave' width='330' height='300' border=0 style='border:none;'> on April 10, 2022, 4:34 pm, in reply to "Re: MZ Buggeration"

Wanted Mr Woodruff

Tonupdave..T.U.D.

Re: MZ Buggeration

Indeed - he was "key" to a lot of succesful engineering solutions

Aparrently some people do get a slot machined for a key in the crank and clutch, but no real need as the as manufactured solution works fine when assembled correctly, and all the components in good order.

Who needs a signature anyway......

Re: MZ Buggeration

Wanted Mr Woodruff

Wrong type of key for the application - Woodruff keys are for alignment, not driving.

If an alternative drive arrangement were required, then a spline would have been better. But that would have required the shaft the be larger diameter, which would have forced a larger diameter for the primary drive gear bearing that runs inboard of the drive on the same shaft (which may not be feasible). Plus cutting accurate splines & broaching the hub would have cost more.

The driving taper is compact, easy to make (i.e cheap ! ) & works well if assembled correctly.

Nigel B.

Deleted

Posted by spriddler <iframe src='https://members5.boardhost.com/classicbikemart/info/user=spriddler' width='330' height='300' border=0 style='border:none;'> on April 10, 2022, 2:20 pm, in reply to "MZ Buggeration"

Wrong thread.

Re: Deleted

Posted by Lannis <iframe src='https://members5.boardhost.com/classicbikemart/info/user=Lannis' width='330' height='300' border=0 style='border:none;'> on April 10, 2022, 3:50 pm, in reply to "Deleted"

That's right... They're Talking About The War!!!

At no time in history have the people forcing other people into compliance been the good guys.

Re: MZ Buggeration

Posted by Stuart <iframe src='https://members5.boardhost.com/classicbikemart/info/user=Stuart' width='330' height='300' border=0 style='border:none;'> on April 12, 2022, 12:26 pm, in reply to "MZ Buggeration"

Hi Andy,

>The handbook recommends that if you have issues in this area then you can use a little fine grinding paste to remove any surface imperfections, or some very fine emery.
>
>No problem with doing that, but I cant see why it hapenned in the first place as the crank and clutch tapers looked in good shape

I don't see any mention of using engineers blue to check the tapers are actually engaging fully - all round and all along? How would the Mk.1 eyeball "look" at two tapers engaging? The less they are in fact, the less use the assembly's going to be?

Hth.

Regards,

Re: MZ Buggeration

Posted by Andy C <iframe src='https://members5.boardhost.com/classicbikemart/info/user=Andy+C' width='330' height='300' border=0 style='border:none;'> on April 12, 2022, 5:54 pm, in reply to "Re: MZ Buggeration"

Some of it may have been down to me not using the correct procedure to torque up the clutch nut - did it the same way on my ETZ and never had any problems.

The clutch hub may have had some damage prior to me assembling it TBH I did not check.

Upshot is that the clutch taper is beyond salvation, so a new one has been ordered, I did run some very fine emery over the taper on the crank and it now looks in pretty good shape - just a few very fine ridges on it.

On assembly I shall be using the technique that Nigel suggested in his response above.

Who needs a signature anyway......

Re: MZ Buggeration

Posted by PantherMan <iframe src='https://members5.boardhost.com/classicbikemart/info/user=PantherMan' width='330' height='300' border=0 style='border:none;'> on April 13, 2022, 9:02 am, in reply to "Re: MZ Buggeration"

Rather like the 'orrible flywheel taper on Morini's then, in that once they've spun on the taper they need serious attention before ever holding on the taper again. In your case I'd say lapping it in was a minimum if there's still ridges showing.

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