REAR BRAKES

Hi all,

so i am working on my 1977 kz 650 which was purchased after being stood for numerous years.

The rear brake, (single disc), was seized solid from the brake pedal pivot all the way through to the caliper. I stripped the brake front to back, i took apart the rear master cylinder and its was full up of solid crud, which has been thoroughly removed and cleaned, the MC bore was not too pitted and was cleaned up, the seal and piston cup where also in good condition and have been re-used in the rebuild.
the problem i have is that the fluid does not seem to be making its way to the hose union, i can completely remove the hose at the MC end and there is no fluid to be seen. On pumping the brake pedal with my finger over the hose hole, i can feel both suction and pressure being generated by the MC piston, however i still get no fluid to appear ?

am i completely missing a trick here?

any help as always gratefully accepted.

thanks,

Matt.

I’ve never experience that problem, but here’s a suggestion you may want to consider. It sounds like you may have air trapped in a way that keeps the fluid from being drawn through when you pump the brake or possible some spec of crud clogging an orifice. If you fill a big syringe like the one in the picture with brake fluid, and connect it to the outlet side of the master cylinder you should be able to charge the plunger, orifice, etc. with brake fluid and if there is any crud clogging the orifice you may dislodge it. Ed

Master cylinder ports plugged still, sounds like. Between the reservoir and the bore Two holes there, are they clear? Did you replace those Old worn rubber pieces? Cups, seals, etc.

Brake Line Bleeders
www.speedbleeder.com/size.htm
www.pingelonline.com/brake_bleeder_kit.htm
spieglerusa.com/brakes/speed-bleeder.html


Brake Lines
www.galferusa.com/html/ss_line_kits.html
inlinetube.com/
www.spieglerusa.com/cfm/brakelines.cfm
www.helusa.com
www.russellperformance.com/metric_two-line.shtml
www.goodridge.co.uk/motorcycle-brake-lines/kawasaki.htm

On the original brake lines, people are finding out that the line will swell up internally, restricting the fluid flow, so you'd be better off with new, SS lines.

Thanks for all the feedback and ideas...I have completely gone through the master cylinder and cleaned every hole and fluid passage in there, I am 100% sure that there is no more crud or debris in there...I did not replace the internal seals or cup as I wanted to get it back on there to use to pump out the seized caliper piston.

Also the fact that I am getting the suction and pressure effect when I hold my finger on the mc outlet indicates that the holes are clear inside...

I could try the suggestion of charging the mc with fluid from the exit hole with a syringe of fluid.

Any other ideas I could try in case?

Thanks again,

Matt.

Open the bleeder valve on the caliper and then try to pump to get fluid through (if you haven't been trying it this way). If you don't bleed the air out of the line, You will never get any fluid through it.

~Clutch

Just an update on the rear mc problem above. I removed it again to triple check it was all clear, interesting thing. - when the mc is upright as in it's intended position on the bike, the piston does not produce much pressure when pushed in, however if I tilt the mc on it's side and depress the piston it produces significantly more pressure.......ideas anyone.

P.s. The mc is clear of debris and all fluid holes and passages are clear.

Thanks all.