Rear Brake Issue help

[ccsct203]

I have rebuilt nearly everything on my my bike.
The issue I'm having is this;
The back brake caliper is dragging on the rotor.
I took the rear caliper was disassembled and that seem fine.
No rust.
I reinstalled the same seals back because they seemed fine
The adjuster is all the way in
could the rear master cylinder be bad?
Could the pressure applied to the caliper not be releasing once the brake is released???
HELP

[andyb]

Yes, certainly.

Within the master is a drainback hole that allows pressure to equalize when the piston is out (resting state).  It mostly makes it so that as the pads wear you don't have to push the lever farther until you get brakes, they should feel the same all the way through.

Easy enough for a bit of crap to get in the way there and cause problems.

The rear caliper is also in a good position to get covered with road crap though, and bind up.  If the mount is bent, if there's crap someplace on the bolts, etc, it's also possible that it can be installed slightly cockeyed too, which will make it drag a bit.

If you've taken the caliper down and gotten everything nice and clean and it still does it (I'm assuming you had to bleed the system when you put it back on), then sure, may as well pull the master apart and see what's going on there.  Possibly a good cleaning will suffice.

[Harvy]

The caliper itself is dragging.......or one of the pads?

Harvy

[ccsct203]

wow....
thanks
Harvy

[ccsct203]

the pads both seem to be dragging

[ccsct203]

i have R1 front calipers
everything new there
Everything was good when I first did my fzr1000 rear wheel upgrade

[ccsct203]

what holds the rear master cylinder together a cir clip?

[Harvy]

As Andy replied mate.......if it was just the one pad, I would have suggested a stuck piston, but as its both sides, Andy's suggesting of a bit of crap in the master fluid return port is likely, or maybe the master piston is not returning/stuck somehow?
I've not pulled one apart on the FJ.....looking at the parts diag, its an internal C-clip.

Harvy

[ccsct203]

i'll look at the parts diagram.
That section is missing in my repair manual

[ccsct203]

Yes, certainly.

Within the master is a drainback hole that allows pressure to equalize when the piston is out (resting state).  It mostly makes it so that as the pads wear you don't have to push the lever farther until you get brakes, they should feel the same all the way through.

Easy enough for a bit of crap to get in the way there and cause problems.

The rear caliper is also in a good position to get covered with road crap though, and bind up.  If the mount is bent, if there's crap someplace on the bolts, etc, it's also possible that it can be installed slightly cockeyed too, which will make it drag a bit.

If you've taken the caliper down and gotten everything nice and clean and it still does it (I'm assuming you had to bleed the system when you put it back on), then sure, may as well pull the master apart and see what's going on there.  Possibly a good cleaning will suffice.

Andy...THANK you

[Harvy]

i'll look at the parts diagram.
That section is missing in my repair manual

Check this site........this for '91 master, but I believe they are all the same.

http://www.boats.net/parts/search/Yamaha/Motorcycle/1991/FJ1200B/REAR%20MASTER%20CYLINDER/parts.html

I like this site for cross referencing.
If you click on the part number in the listing, A new window will show you every Yamaha bike this part was used OEM.

Harvy

[andyb]

Ok, THAT is a cool fische.. I like that...

[ccsct203]

I'll disassemble it tonight.
It's dragging way to much even to ride a short distance....

I'll try cleaning it first and look at the cylinder bore.
at the price of $72 for a rebuild kit a used ebay unit looks much better

[jvb_ca]

Thanks Harvey...good find...awesome site. I am always checking to see what else certain parts are used on. And I can even search for parts for the fishing machine now...


Cheers...Jake

Check this site........this for '91 master, but I believe they are all the same.

http://www.boats.net/parts/search/Yamaha/Motorcycle/1991/FJ1200B/REAR%20MASTER%20CYLINDER/parts.html

I like this site for cross referencing.
If you click on the part number in the listing, A new window will show you every Yamaha bike this part was used OEM.

Harvy

[racerrad8]

The best way to determine if it is a master cylinder or caliper problem is by opening the bleeder at the caliper and seeing if there is a small squirt of pressure.

If the master cylinder return port is clogged or partially blocked then the system will maintain the pressure. By cracking the bleeder screw at the caliper you should see a small squirt of fluid. You can check this several times if needed. Close the bleeder, pump the brakes several times and release. Now go back and crack the bleeder to see if you release the pressure.

If there is no pressure then the master cylinder is fine and the caliper is the problem. You might also check the rubber hose and make sure it has not de-laminated internally and has created a flap that is blocking flow.

Sorry, I don't have a source for that rebuild kit...

Good luck, Randy - RPM