Braking issue

[ksizem12]

The only way that I think that could even be possible, is if the pinhole causing the air leak somewhere in the brakes is closing up once things get hot, temporarily allowing pressure to build from multiple pumps, as even with air in the line pressure will still build, at least to a point, possibly enough to give you a poorly functioning rear brake.
I would rebuild the master cylinder and caliper, and buy a new stainless steel rear brake line.
Brake maintenance is important.
That is also not throwing parts at a problem, as if one part of the system fails from age, then the others need the same attention.

Definitely gonna do a teardown on the rear caliper. I’m leaning towards air getting into it as well I do already have steel lines

 

[Kiwi Rider]

I'm a bit late to the party here, but here goes . . .
The rear caliper has 2 bleed nipples, you will need to bleed the INNER bleed nipple on the inside of the caliper, I guarantee it has air trapped in the back side piston cavity of the caliper, I've struck this before.
The front rotor or rotors have excessive run out causing the 'shudder' you refer too.

 

[Kiwi Rider]

The only way that I think that could even be possible, is if the pinhole causing the air leak somewhere in the brakes is closing up once things get hot, temporarily allowing pressure to build from multiple pumps, as even with air in the line pressure will still build, at least to a point, possibly enough to give you a poorly functioning rear brake.
I would rebuild the master cylinder and caliper, and buy a new stainless steel rear brake line.
Brake maintenance is important.
That is also not throwing parts at a problem, as if one part of the system fails from age, then the others need the same attention.

I've had a situation similar where a customer brought his GSXR into the workshop I was at, and complained he had no rear brake but would pump up a little with multiple foot stabs on the pedal.
He said he had bled the rear caliper and no change to it.
I looked at it, bled BOTH bleed nipples (2 piston caliper) and sure enough, the inner piston bleed nipple had not been touched.
I put a bleeder hose and bottle on the inner nipple, cracked it open, pushed the pedal a few times and fluid eventually came through the hose.
The rear brake acted normally after that.
It took me 20mins to sort that brake, and the customer was stunned!
He had spent hours on it, but never thought to bleed it out BOTH bleed nipples.
Lesson learned lol.

 

[Kiwi Rider]

@ksizem12 . . . . Hey bud, shouldn't that adjustable threaded end on the brake torque arm have a locking nut fitted to it?

 

[Kiwi Rider]

@ksizem12
Here’s a couple pics of the caliper to explain what I mean about the other bleed nipple. . .

Below . . the circled nipple.

 

[jellyrug]

@ksizem12
Here’s a couple pics of the caliper to explain what I mean about the other bleed nipple. . .

View attachment 1682335

View attachment 1682336

Below . . the circled nipple.
View attachment 1682337

Those are big nipples. Always thought Busa was female.

If that bike came to me, I would have both wheels off, start at point A and work myself through to point Z, checking every single detail and replacing what is not perfect as I go along.

 

[Kiwi Rider]

Those are big nipples. Always thought Busa was female.

You see what I did there?
Some call them “bleed screws”… I prefer the nipple terminology myself.
Isn’t great how the rear caliper has 2 nipples and not just one… double the fun lol.

 

[CallieWilkinso]

It sounds like either a seized brake piston or the pads are jammed, or the pad sliders are seized.....

Hello all I’m hoping someone can help. I changed my back tire out and now I have no rear brake. It’s almost as if the piston is not backing off of the caliper. I’ve bled the brakes to verify fluid and pressure but still no luck only when I first start out I have light brakes but after a couple miles my pedal is gone. I literally have to stand on the rear brake to get a little bit of slow down. Also under hard braking with my fro t break I’m getting a front end bounce or shutter. Also happens sometimes when I’m in first with higher rpm’s and let off but not as much as with the brakes. Please help.

Speed Test​