Splitting the master cylinder

[DeeG]

I have the 13mm Magura m/c with the round reservoir.  Aside from smacking it numerous times with a rubber mallet, is there any other good way to break the m/c portion off the handlebar mount?

I'm terrified of breaking it.

[Tony Smith]

Remove M5 bolts and soak in 50~50 mixture brake fluid and Acetone (don't get this anywhere near the irreplaceable plastic).

my wife wanted a "round" master cylinder to keep her 79 R65 more "genuine" (Dog knows why cause its already got a 87 R80 engine in it), that's when I discovered you cannot buy a new plastic reservoir for them, you can however buy a brand new master cylinder from motobins the last time I looked.

[DeeG]

Got the bolts removed and its like its glued together. I suppose it would be that way after 35 years.  I'll get it to soaking.  The paint needs to come off as it is. 

I looked at the replacement m/c....$460US eeek!  I will if  must, but I'd love to keep the R45 as original as possible.

[Bob_Roller]

The reservoir is bonded to the metal part of the master cylinder not meant to be separated .

[georgesgiralt]

llo !
The BMW classic shop shows the round M/C as NLA... Last was 160 Euro apiece.
SO maybe you should ask another dealer in your country...
Oh, and they show it with 16 mm dia only. So wooden brakes are on ;-)

[Bob_Roller]

Dee, I think you're going to need to do some online searching for this part, doesn't look to be readily available .

About all I can find, is 16 mm diameter master cylinders with round resevoirs .

[DeeG]

Bob,

I don't want to take the plastic reservoir off. The whole thing looks like two metal parts bolted together. The metal part with the plastic reservoir on it and the part that slides onto the handle bar.

Looks like I would have to split them to replace the plunger and seal.

[Bob_Roller]

OK, sorry, I thought you wanted to remove the plastic reservoir itself .

[DeeG]

OK, sorry, I thought you wanted to remove the plastic reservoir itself .

I wish!!  That would make stripping and painting it so much easier. :-)