REAR BRAKE MASTER CYLINDER

Hi all,

i stripped my rear brake master cylinder on my 1977 Z650 C model.
The bike had been stood for many years and predictably as a result the MC was full of crud, after a lot of cleaning an honing of the bore the cylinder is back together and looks good to go, however i am getting nothing out of the MC when its back on the bike, when putting my finger over the outlet of the MC i feel some pressure, but get no fluid at all to come out of the outlet.

i removed and re-stripped the MC and all the fluid passages are clear.

there is one machined hole that seems as though it should lead somewhere but does not..
I have attached a photo of the master cylinder and also a close up showing the hole i am speaking off, should the center hole lead into the MC bore like the one below it?

it seems like it should but it seems jammed with something as tough as metal as i can push a small pick as hard as i can into the hole with no result and also from the little view i have of the bore itself i cannot see an obvious hole, either blocked or not.

if anyone has had a similar problem or any ideas, please let me know.

thanks, matt.

#6 is listed as "BOLT", and looks like it goes into that hole you're asking about. Maybe it just needs to be plugged and forgotten? Others may have some better info for you....

this hole you are referring too? (picture)
looks like a pilot drill mark when machining

how are you bleeding the brakes? you might have a lot of air in the line and thats why your not getting anything out of the master cylinder. you may want to try a vacuum bleeder, they work great.

Perhaps concerned with the wrong holes.

Should be two holes at bottom of the reservoir (one larger and one smaller).
Larger hole supplies fluid to bore where piston moves back and forth.
Smaller hole allows pressure relief upon releasing brake by allowing fluid return to reservoir.

The issue may arise where one of the holes is obstructed.

Good Fortune!

Patton and all, thanks for the help..

Could you confirm for me please Patton which two holes you mean...are you refering to the two holes i pictured in my photo?

If i could see inside another MC i would be able to work out if both of the holes should go through the bore..

I cannot think what would block one of the holes so much that i cannot push anything through, the next thing i can think of is a small drill bit but do not want to do that in case there are not supposed to be the two holes into the bore.

I cannot see why the hole is there if it has no purpose and its at the stage where there is almost daylight into the bore from this machined hole.

Its a real puzzle to me...

does anyone know where i could get a picture or diagram of the actual intended flow of fluid within the MC?

www.autoshop101.com/forms/brake02.pdf
Generic, but explains it very well.

This thread may help.

www.kzrider.com/forum/5-chassis/457395-c...stercylinders#457395

Good Fortune!

Do you have or can get the welding tip cleaners? They come in a fold out kit, designed to clear clogged torch tips. Try a wooden toothpick first as the clog may be soft.