Location of the Rear Master Cylinder Tiny Hole ( that needs to be clear of debris )

[Guest]

having some trouble with the rear brake on my project bike, a 1979 GS750L. hadn't been run in years, but in pretty good shape overall. a smidge over 18K miles.

i can't get any fluid to move from the rear brake fluid reservoir to the master cylinder. have tried operating the brake pedal of course, and also the "gravity feed" method, where one ties the brake lever down and waits over a few days/week for the fluid to migrate into the m/c.

i plan on disassembling the rear master cylinder for cleaning and possible rebuild kit installation, and plan on ensuring the tiny hole is clear but where is it? i've rebuilt front m/c on cb750's before, tiny hole is easy to find.
thx,
bob p

[Steve]

If you look on the side of the M/C, you will see the fitting where the hose from the reservoir fits. Remove the fitting, look inside.

There is a larger hole (maybe 2mm) near the bottom and a much smaller one (0.5mm?) near the top. Both of them need to be clear.

.

[standswithabeer]

excellent!
many thx,
bob p