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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: kris on March 23, 2015, 12:14:59 PM

Title: Rear Brake Pedal/ Master Cylinder Re-Assembly
Post by: kris on March 23, 2015, 12:14:59 PM

Hi all,
Am I missing something here? I have my nippled adjustable bolt pushing straight back into the cylinder tube. Please see photos and that will help explain. Is there a small part that goes at the end of the piston assembly? Or is it just the adjuster nut pushing on the circumference of the piston...through the rubber boot?

Thanks....seems confusing to me.

Title: Re: Rear Brake Pedal/ Master Cylinder Re-Assembly
Post by: The Mighty Gryphon on March 23, 2015, 12:44:14 PM

I'm pretty sure the only thing missing in your photo is the large rubber dust seal/boot that goes over the end of the master cylinder.

Title: Re: Rear Brake Pedal/ Master Cylinder Re-Assembly
Post by: kris on March 23, 2015, 12:54:21 PM

Thanks Jim. I guess the nipple end simply receives the end of the boot. The nut then makes contact with the piston through the rubber...is that your read on it? It seems odd to have the rubber as the interface between the nut and the piston, for wear reasons and a slight reduction in direct energy transfer. Not the slickest setup I've ever seen.

Title: Re: Rear Brake Pedal/ Master Cylinder Re-Assembly
Post by: The Mighty Gryphon on March 23, 2015, 01:06:05 PM

Here's a picture:

Title: Re: Rear Brake Pedal/ Master Cylinder Re-Assembly
Post by: Inge K. on March 23, 2015, 03:20:54 PM

In addition to the rubber boot, you're missing the part in the picture....it should be between the
adjusting screw and the piston.

Title: Re: Rear Brake Pedal/ Master Cylinder Re-Assembly
Post by: kris on March 23, 2015, 04:07:32 PM

Thanks Jim and Inge. I am attaching a photo of the Magura rebuild kit. It shows a variation of the piece that Inge posted a photo of. Inge, does the flange of that piece rest on the edge of the piston? I ask because the Magura piece looks like it might be able to fit inside the piston. I am going to fabricate a replacement piece and just want to know what direction I'm heading in.

PS - I have the boot....just didn't put it in the photo

Title: Re: Rear Brake Pedal/ Master Cylinder Re-Assembly
Post by: Inge K. on March 23, 2015, 05:28:48 PM

The part to the left of the boot have the same purpose as the one in my Picture, and they are mounted
inside the piston......only the flange with the concave seat is on the outside, with a small opening behind
the flange.

But the part in your picture is usually used together with a 12mm piston, your model should have a 13mm
piston...unless the rear master earlier have been changed.

Also I see a piston from a 20mm front master in the picture, this isn't used on your model either.....unless
you have a master from a 4 valve model.