The piston got stuck inside, so I’ll do an OH. (I’ll replace the parts)
So here’s the thing…
When doing a full stroke during fluid exchange, I noticed something felt spongy.
Hmm, that’s odd—it feels mushy?
The piston got pushed and never came back.
When I remove the snap ring and take off the arm, it looks like this.
The piston can’t come back from the other side.
The return spring can’t overcome“corrosion and seizing”that’s happened.
It’s a good thing this happened during fluid exchange…
If it had happened during a full brake application…that would’ve been scary.
Bikes are dangerous…I think about it every day.
The inside of the cylinder is clean. This can be reused.
The master always has“return ports”.
They’re incredibly tiny—usually 0.5mm or less.
Corrosion or debris can clog them, and dirt buildup can narrow the hole.
Air blowingoften can’t remove it, sousing a micro drillto carefully clean from a smaller diameter is more reliable.
New vs. old comparison.
You can see the one on the left is quite dirty.
This part got dirty and stuck.
You can see the difference in the master cup“umbrella opening”between new and old.
As it’s pushed and the cup opens,“hydraulic pressure”is applied, so pressure loss is minimal.
However, when the cup gets old and“shrinks,”the umbrella opening“develops some lag,”which I think“leads to soft feel and lag.”
Hmm, nowadays the cup isn’t pre-installed…
I just put it in by hand, but…some people might not be able to.( ；∀；)
And that’s how it turned out beautifully.
Let’s replace the hose and tank while we’re at it.
Now let’s finish up the rear caliper.
Like the front, the rear caliper condition is good.
The seals don’t show deformation, but they’ve become quite hard.
I’ve finished the inside of the caliper like this.
One piston hasn’t arrived yet, so it’s on hold.( ﾟДﾟ)
Parts don’t arrive quickly these days…
I’m used to it, but“it’s difficult”to be honest.
Putting it on hold for now.
