Rear Brake Master Cylinder

Switching rear shock spring (again) today and decided to 'quickly' change the rear pads - not desperate but I already had replacements - so clearly 'just a 5 minute job' (NOT).... Obviously needed flat blade to open the new pads to fit back on the wheel (& I checked reservoir didn't overflow).

When it was all back together I didn't have any rear braking at all (I did before !).. Tried bleeding it pushing foot lever & tried vacuum pump whilst doing the same but couldn't get any fluid out beyond 1/4 inch into bleed line from rear caliper nipple (in fact if I left the bleed nipple open the fluid went back in when brake lever returned to normal)... All stripped down & seems the master cylinder doesn't want to get any fresh brake fluid from reservoir - if I push it in with pencil and then hold the outlet pipe (finger); it forms vacuum that doesn't get released through the reservoir feed holes .... Noticed somebody had similar problem GT and it was failed rear MC.

Just checking any other experience before I start looking for new rear MC ?? Can't find any kits for these & despite getting the circlip out I can't get the nylon innards out without buggering it anyway ...

Replacement new MCs in Europe look like rocking horse shit availability and expensive pricing €124 plus :-(.  I'll change the rear brake line at the same time as it's looking tired and that only costs £31 from HEL

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I would try eBay. It's a universal master cylinder used on a plethora of Ducati's.

And Aprilia's, and Yamaha's and ................... Brembo universal.

Thanks for guidance - it was a generic part and cost £66 delivered to house from Demon Tweeks. All fitted back, fresh brake fluid and all good. Lessons learned in case it helps others:
1. If you use the 'stand on rear brake lever while leaning over bike and removing/retorquing rear wheel' method; make sure the caliper is on the disc
2. The rear master cylinder is a 13mm std Brembo side exit 40mm (between bolt holes)...loads around but not stated they'll do a GRiSO.
3. If you order replacement brake pipes you need to take the old one off and measure EXACTLY the C-C length cos there's nowhere to hide slack and nowhere to use less than original length - some dickhead thought he could run a piece of string along fitted line & get accurate enough measurement (don't ask!)....also the HEL fittings are different to OEM (especially the 90 degree on caliper) and the original are very tight fit in first place - the HEL 90 degree would have been a struggle.  That's £31 in bin.
4. Fit and fully torque the brake line to master cylinder before you fit the side panel....even after 25nm torque there's still only enough room to run a fag paper between banjo and the casing. Using pipe through the plate hole helps support it all while you assemble it.

Can get back to rear shock spring rate testing now !

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Jeez ; haven't heard that "Fag Paper" expression in at least 40 years. makes me think of my grand fathers.

If you can slide a fag paper in, it's too loose.
If you can't slide a fag paper in, it's too tight.