Etz 250/251 master cylinder

[Blurredman]

Anyone know the seal measurements for the master cylinder? The seal that prevents the brake fluid from leaking past the lever...

I recently rebuilt mine with a kit but the new seal is leaking. There is one on eBay but far too overpriced..!!

Thank you..

[Guesi]

Do you you mean the MZ or the GRimeca model ? Both were on ETZ 251 models...
If you mean the MZ version with the round cover, there are 2 Versions.
The piston size is different.
The old ones had 12,65 mm diameter
the later models had 11,40 mm diameter.

Most of the available repair kits are for the earlier model with 12,65 mm piston.

[Blurredman]

It is an MZ type. Bought it from a chap on this forum.

I would say that it would be the older of the two types, as the replacement seal seems to fit well enough (though not sure why it leaks).

Gusi. You sell these seals? Do you get many people saying they leak? I have looked through the internet and found that several people have found that they are susceptible to leaks.. ?

[Guesi]

Hello
I sell repair kit for the "big" piston type.
The problem lies in the construction.

The big sealing rubber is, as the name says, made from rubber.

When you press the lever to the piston, the piston is pressed to the housing.The rubber does not have enough guidance to keep the piston away from the side of the housing.
So the housing wears out during the y<ears ...

The repair kit I have uses an oil seal ring which is more stable than the rubber. Thus the piston is guided better inside the housing...

But if the housing is worn out it will leak even after the repair...

About 80% of the leaking master cylinders stop leaking after the repair...
The other 20% need a replacement of the master cylinder...

[Blurredman]

Anyone know the dimensions?

10x20x7 ?

[Guesi]

It must be brake fluid resistant. And it is 10x20x8

[Blurredman]

Great. All installed and seems to be working grand. No leaks.... Yet