1979 gs850 rear brake bleeding.

[joe penoso]

I am working on an abandoned 41 year old bike. Rebuilt REAR caliper, then rebuilt REAR master cylinder( K&L). REPLACED REAR HOSE WITH oem ONE.
FILLED ROUND CYLINDER WITH DOT 3. Started pumping brake pedal, few small bubbles..........after 15 minutes nothing. Help what do I do next?
Thanks
joepenoso

 

[Steve]

Start by priming the master cylinder. Remove the hose from the top of the master cylinder. Keep a rag handy to wipe up any spills. Press a finger lightly over the outlet, press the pedal down. Push harder on your finger, let the pedal come up. Repeat until fluid comes out the hole. Put the hose back on, move to the caliper. Put a clear hose over the bleeder, have it drop down into a catch bottle that has enough brake fluid in it to cover the end of the hose. Repeat the basic bleeding process: open the bleeder, push the pedal down. Close the bleeder, let the pedal up. Repeat until fluid appears with no bubbles.

.

 

[joe penoso]

Thanks for your advise. Guess I,ll go back to the hot garage and sweat some more....lol

 

[joe penoso]

It appears after bleeding as advised above. I removed side hose that leads to brake fluid container, pumped brake pedal fluid was being forced out side outlet instead of top banjo bolt.
WTF? Time to take it apart and retrace my steps.
joepenoso

 

[bwringer]

It appears after bleeding as advised above. I removed side hose that leads to brake fluid container, pumped brake pedal fluid was being forced out side outlet instead of top banjo bolt.
WTF? Time to take it apart and retrace my steps.
joepenoso

Why did you remove the side hose? You need to leave the reservoir and hose in place or you're just going to suck in air.

 

[joe penoso]

Why did you remove the side hose? You need to leave the reservoir and hose in place or you're just going to suck in air.

When in place the DOT3 wasn't being pumped to the top. Took side brake fluid feed and fluid shot out past back wheel. Looks like Master cylinder pumping sideways
to reserve not up towards banjo bolt.

joe penoso

 

[bwringer]

When in place the DOT3 wasn't being pumped to the top. Took side brake fluid feed and fluid shot out past back wheel. Looks like Master cylinder pumping sideways
to reserve not up towards banjo bolt.

joe penoso

That's normal, and probably a good sign most or all of the air is out. When the piston first starts to move, you'll get a pretty good jet of brake fluid from the compensation port. You see the same thing on front master cylinders; if the lid isn't on the reservoir, it'll squirt out the top pretty far when you pull the lever and get all over the place.


FWIW, I've never had much luck at all with aftermarket brake kits. It looks like the OEM Suzuki "Piston & Cup Set" is still available for the master cylinder, and the OEM seals are available for the caliper. although the pistons aren't available.

It's possible the K&L stuff is working fine and there's some other problem like an assembly error or corrosion, etc., but it's impossible to say without parts in hand.

 

[joe penoso]

Son of a gun, I found it! Rear master cylinder spring has a wide and narrow side. Wide side goes in first. Rubber bucket shaped thing goes on bottom of spring. Someone before me took it apart and incorrectly put it together. I bought another rear master cylinder but someone else got to it first and it wasn’t put in correct order. Researched on this sight. Micro fish for part order was unclear for order assembly. Searching past files I found in May 17/2020 someone had same problem and 2bBRacing provided pictures of correct order and all became clear! Thanks to everyone for their efforts and help
joe penoso