Another can't pressure brakes question.

**omamari** · 23rd May 2015, 12:22

Yup, can't do it. FXR. Last race I realized my front brake wasn't releasing nicely. Front wheel would barely turn when it was raised off the ground.
Took off caliper, pulled out pistons, really dirty. Cleaned pistons and cylinders. Didn't replace seals. Put back in. Can't get any pressure in the lever. I've raised the caliper up high. Do the squeeze open bleed techniques, nothing. Fluid comes out the line, I got air initially, but now nothing but fluid. Pistons aren't moving at all. I think master is ok as I had solid braking during the race. What am I doing wrong here guys?

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**speedpro** · 23rd May 2015, 12:27

FXR, says it all!

**Drew** · 23rd May 2015, 12:43

The trapped air is at the master.

You need to angle the bars so that the fluid port in the master is higher than the banjo bolt. Then pull the lever ever so slightly a bunch of times. You'll see the air come out.

**omamari** · 23rd May 2015, 13:09

Sorry, i don't quite grasp. I'm not sure what the fluid port is, but I guess I just need to have the banjo bolt being the lowest part of my MC?

**omamari** · 23rd May 2015, 13:11

Originally Posted by Drew

. You'll see the air come out.

Should it come out through the master?

**omamari** · 23rd May 2015, 13:19

Drew, legend. I have a little pressure now so it moves the pistons a little bit. But the pistons just get sucked back in again. Can't get them to stay out and take up the gap between pads and disc

**nodrog:Me** · 23rd May 2015, 13:22

Originally Posted by omamari

Drew, legend. I have a little pressure now so it moves the pistons a little bit. But the pistons just get sucked back in again. Can't get them to stay out and take up the gap between pads and disc

Pull the caliper off, remove the pads

Pump the pistons out as far as you dare, clean and apply rubber grease.

the seals are pulling the pistons back in by the sound of it

**omamari** · 23rd May 2015, 13:24

They are, when I reinstalled I did not apply rubber grease. In fact, never heard of it

**Drew** · 23rd May 2015, 13:36

Originally Posted by omamari

Drew, legend. I have a little pressure now so it moves the pistons a little bit. But the pistons just get sucked back in again. Can't get them to stay out and take up the gap between pads and disc

Yeah, banjo bolt the lowest bit when bleeding.

Did you take the seals out when you cleaned the caliper? Sounds like you've got them in the wrong way round. The piston doesn't actually slide through the seal when braking. The move through as the pads wear, but most of the time the seal actually rolls to allow the piston to move the pad to the disk.

They are ever so slightly tapered on the piston face to accommodate this.

**FJRider** · 23rd May 2015, 13:38

Originally Posted by Drew

The trapped air is at the master.

You need to angle the bars so that the fluid port in the master is higher than the banjo bolt. Then pull the lever ever so slightly a bunch of times. You'll see the air come out.

Cruiser style bars were renown for needing this .. the angle of the dangle ... so to speak ..

Nodrog is on to it ... most likely a bit of grit in the fluid jamming the piston. Often best to pull the pistons out and checking for damage ... and replacing the entire amount of fluid (new seals never hurts [except the wallet] either).

**omamari** · 23rd May 2015, 13:40

I've got them in correctly. It's feeling better now I've got it on the actual disk. I had a bit of ally spacing them when caliper was raised. It was a bit too thick.

Interesting about the rolling.

Thanks heaps guys. Now, seeing as I've got some fresh fluid, KTM time. ..

**omamari** · 23rd May 2015, 13:42

Originally Posted by FJRider

Cruiser style bars were renown for needing this .. the angle of the dangle ... so to speak ..

Nodrog is on to it ... most likely a bit of grit in the fluid jamming the piston. Often best to pull the pistons out and checking for damage ... and replacing the entire amount of fluid (new seals never hurts [except the wallet] either).

Pistons were a bit rough, but passable. Yea I was surprised they were so expensive.

**Drew** · 23rd May 2015, 13:46

Originally Posted by omamari

Pistons were a bit rough, but passable. Yea I was surprised they were so expensive.

Outfit down here makes them to order. Cost me $35 for two seals last time I got some.

**FJRider** · 23rd May 2015, 13:53

Originally Posted by omamari

Pistons were a bit rough, but passable. Yea I was surprised they were so expensive.

Passable ... but still not working properly .... but only a bucket ... right .. ??

DIRTY pistons indicate fluid contamination.

My advice ... change the seals AND fluid.

Blow out the line of all fluid and clean all parts. Then replace with new fluid ...