Das MZ Forum für MZ Fahrer

Hi

The big "mutter" on the cylinder goes loose all the time, how do I fix it? I have tried tigthening it really tight, but still does not work.

May be the thread is destroyed. Or have you bought some new parts, that not in right conditions?

Thread is good, last year I got it to stay but had engine out this winter, now can't get it to stay again.

If you use the right tool "Hakenschlüssel" you will fix it. I normaly use a hammer when the engine is warm to pull it stronly on. Other prefer a tube on the Hakenschlüssel to get a higher torqe.

Have a "Hakenschlüssel" but they just bend when I tighten Will try loctite and teflon tape.

I think the problem is the tool, you need a real one.

clean the threads...
then tighten the nut really hard, this goes against everything you know about nuts and bolts. just tighten it *properly*. best results of course with an adequate tool for the job.

g max ~:)

My friend Joerg usually puts a bit of tube over the tool and then stands on the other end ... about 100 kg ...

There is another option, which is to make some cuts in the nut face with a hacksaw, so the nut can adjust to the thread/exhaust more tightly (usually used for thread repairs). This will result in more friction.

If the nut really does unscrew you may think about pinching a hole and securing it with wire to a hole in one of the cooling fins

Andy

wow

tighten it once the machine is warm

Hello,
I had the same problem for many years. Last year I put some exhaust repair paste between cylinder and exhaust and then tightened the nut to "correct" torque ->This is what happened. But it did not come loose anymore I used a 1,5 metre tube to get the right torque. Crappy tools those original MZ-tools. I used same kind of tool made for Ariel to get the nut open. That was made from steel plate.

Regards
Teemu

Hi Teemu,
attention! You would't be the first to destroy the threads (which would be very annoying).
Clean the parts (toothbrush), apply some ceramic grease and screw the nut in *by hand* until the end. If it is not possible by hand, threads are dirty or you put the thread wrong (like probably someone before you might have done it). Try again until it is possible (you may take away the exhaust bend for the try).
Now the exhaust bend (separated from the pot) should be fixed already. If you can wiggle it, take it apart and make the face side, that goes into the cylinder, really even.
Mount again, then the silencer fixation below the engine, then the rear strap, all hand-tight.
Only at the end when all three silencer screws are hand-tight, you tighten the cylinder nut with 150 Nm (!), then the front and at last the rear bolts.
Done this way, it shall be gas tight and won't get loose.
Greets
Carsten

Hello,
From my original cylinder the threads were destroyed. I had a problem with the exhaust when we brought the bike from Vietnam to Finland. It was behind my fathers car (Land Rover Discovery) and the car had bounced during the trip so that the tow bar had smashed the silencer. I had to take the exhaust off on regular base to repair the silencer until I got a spare one. That is why I used the repair paste. Now I have a new cylinder (300cc) and I have to be more careful with the threads.
Unfortunately in the early -90's there was no such thing as internet or forums like this one.
I have had more trouble with the silencer as it hits the rear shock absorber.

Hi,
Vietnam, wow. The exhaust cylinder nut will rarely be destroyed by external force, but always by forcing the wedged nut into the cylinder alloy.
For the problem that the pot touches the shock absorber: try to rotate it slightly around its axis.
You may also reverse the rear fixation rod: I guess I remember that it is not strictly symmetrical. Try to mount it upside down. Or bend it

I tried cleaning it with "grease-remover" spray today and then some teflon/threadtape wound around the exhaust bend, and then around the nut. Should keep my engine cleaner as well.

Do you guys run with a coppergasket in the cylinder? I have heard some do and some don't.

I don't. But I thought about an Aluminium profile ring as a gasket, that also fills the bevel at the pipe end for a smooth passage to the cylinder. Fine tuning

Hello
The best "greasing" material when heat plays a role is by my experience powder of graphite.
A graphite pencil (in Germany: B6 Faber Castell) used by drawers will easily serve for the same purpose.
How to fix the screw?
1. Clean Screw and thread.
2. First time to turn the screw: do not mount anything else before the screw will get fastened. When it has 2 turns beginn to
mount the exhaust pipe. But do not fix strongly before the srew yet isn't hard turned into the the cylindre's thread.
3. Trick to turn: always turn for the first moment to the left, in the wrong way. When it does a quite click then it s the beginning of
the thread and you turn now to the right. (the same to do with the spark plug)
4. To fix it with force: use a tube as Motorrang explained. Other way: I use a cranked ring spanner (gekröpfter Ringschlüssel) to
enlarge the arm of lever. (yesterday on my way back to Dresden I had to do so in Spremberg. The machine was blowing by due to to an unfixed srew of the exhaust. Later it ran better!!)
Michael