Soft brakes after bleeding system

[bobross]

this is a continuation of a series that started with "Rotational Noise" followed by Rebuild Brake Caliper.

Summary. The rotational noise was the nearly gone rear brake pad and scored disc. BBought the new Brembo disc and new pads from Carpimoto at big savings over going to dealer. Installed all.

Initially not getting fluid through the bleed screw and wondered if the caliper was bad. Just needed to keep pumping. Got it to work. In the process, busted the rear brake hose. So ordered new SS Spiegler hoses.

To do the hoses, I figured I would need access to the ABS system to bleed, so took off the bodywork and removed the tank. Installed the new brake lines, and new pads in the front.

Also, as long as the tank was off, put a new fuel filter in the tank, new air filter, installed the quick disconnect fuel lines. New battery, as the old one was 5 years old (battery from Interstate, higher amp/hours and higher CCA THAN bmw BATT, AT HALF THE COST). Even bought a AF-xied unit and hooked it up. (it has been raining steadily here in Oregon so is a good time to do all this stuff, and I have a nice warm garage to do it in.)

CURRENT PROBLEM: SOFT FRONT BRAKES. I have bled this several times. Rear brake is taut, Front is soft, unlike before I began all this work. I have bled it from the screw on top of the ABS II unit, and at the calipers, both places by opening the screw and squeezing the front brake handle, keeping the reservoir topped up. No bubbles. Don't see any leaks at any of the fittings. But, pushing the bike around in the garage, and squeezing the brake, the front brakes grab, but are really soft in comparison to before.

Will this go away, or have I missed something.?

[giarcg]

I, and have read accounts from others, have experienced front brake sponginess following flushing that has eventually gone away. Some have claimed that "microbubbles" need to work their way to the master cylinder. I don't know about that but I do know that the condition dissapears in a matter of hours.... overnight for sure.

I also have found it necessary on some bikes with clip ons to lean the bike hard to the left to let air escape the banjo fitting on the brake master cylinder (lean to the right for the clutch). Don't recall if it was ever necessary on the S but definately was on my Ducatis. Loosening the banjo while appling the brake will achieve the same thing. Just tighten it before releasing the handle.

[N41EF]

I worked on a K bike with ABS 1 that didn't want to bleed, felt mushy. Try taping the abs unit and calipers with a rubber mallet then bleeding them again. I kind of jars any air bubbles loose, and to the bleed points. Are your front hoses good? Might also cause mush.

[BigDav]

When I installed my lines I followed the service manual and installed blocks in place of the brake pads when bleeding.

My front brakes have never been better. Nice and firm.

[giarcg]

Originally Posted by BigDav

When I installed my lines I followed the service manual and installed blocks in place of the brake pads when bleeding.

+1

I leave the pads in the calipers, push the pistons in and use window shims between the pads to hold them there...works great.

[JimMoore]

If it's rideable, ride it around for a little while. That has worked for me in the past.

[Lowndes]

Originally Posted by jimmoore

if it's rideable, ride it around for a little while. That has worked for me in the past.

+1

[RodPlunger]

One trick I found when bleeding an older Honda, was to remove the master cylinder cap then GENTLY squeeze the brake lever in slightly. Just enough to see the fluid move. Then, tie off the brake lever at the point you have drawn it to. Leave it overnight. The idea is that all the little "microbubbles" will have a way and a place to leave the brake lines and fluid. Has worked like a champ on systems without ABS. So, the ABS might throw it off. But, if you have it sitting around in the garage, it's an easy, risk free job to try.

[bobby11]

I just finished putting new SS lines on my 09r11s. Could not get the air out of the front until I turned the handlebars back and forth and then pulled the brake lever in and tied it off overnight. I think the handlebar turning helped dislodge air trapped at the bleed screws and allowed that air to get up past the banjo fittings.

[Nitro]

Best 17 bucks I've ever spent!

https://www.ebay.com/itm/Car-Hand-Held-Vacuum-Pressure-Pump-Tester-Set-Brake-Fluid-Bleeder-Bleeding-Kit/132240926489?epid=2186773762&hash=item1eca2c6719:g:ucwAAOSwWLFZo6z0

[bikerfish1100]

What bobby11 said.
After bleeding, turn bars full left, and strap the brake lever as tight to the grip as possible. Leave overnite.

[tjs]

+1

[BadToTheBown]

Originally Posted by RodPlunger

One trick I found when bleeding an older Honda, was to remove the master cylinder cap then GENTLY squeeze the brake lever in slightly. Just enough to see the fluid move. Then, tie off the brake lever at the point you have drawn it to. Leave it overnight. The idea is that all the little "microbubbles" will have a way and a place to leave the brake lines and fluid. Has worked like a champ on systems without ABS. So, the ABS might throw it off. But, if you have it sitting around in the garage, it's an easy, risk free job to try.

+1 works every time so far

[Chris Canning]

Tie off is a bit dramatic a half decent elastic band will do just fine.

[BadToTheBown]

tie-wraps also work...

[RetiredMech]

Highly recommend buying a Mighty Vac vacuum bleeder. Solves all of the problems.

/www.ebay.com/itm/Mity-Vac-Vacuum-Pump-Brake-Bleeder-Kit-MV8000-Free-Shipping-And-No-Tax/222748667459?epid=1211819273&hash=item33dcdaee43:g:lUsAAOSw4aBaKzOY

[rhenthar]

If you use a vacuum bleeder, especially the air-powered kind, it'll suck so hard from any point in the system, it will actually draw the pistons in on both sides. This means if you use the ABS bleed point, it's pulling fluid FROM the calipers, instead of through them.

Here is the key: Hold the brake lever fully while doing this. It cuts off the supply to the reservoir, meaning 100% of the suction is useful. The fluid level will not fall so long as the lever is all the way in, so you can just let your bleeder go to town drawing in all the fluid from the calipers and retracting the pistons fully. You will have to pump the lever slowly after all this is done, to extend the pistons back out. Figure 6-8 pumps, so you'll be adding fluid constantly at that point.

Repeat that a few times, and you'll get every last bit of air out.

Some air will come in around the threads in the bleeder if you're doing this on the caliper bleeders, and for this reason afterwards I do a few traditional bleeds: squeeze lever and hold - loosen/spray brake fluid out a hose on the bleeder - tighten bleeder - let go of lever. The ABS bleeder has an O ring that stops this effect and keeps the bleeder sealed despite it being loose.

Some of that is mitigated if you take the bleeder off and put some teflon pipe thread sealing tape around the threads, but make sure it's high enough up not to allow any loose tape to enter the brake system. I allow a couple of millimeters of bare metal to show at the bottom where you thread it into the caliper.

Remember in a state of lower pressure (suction) all air bubbles grow in size and generally move around more easily and faster.

[Lowndes]

"...if you use the ABS bleed point, it's pulling fluid FROM the calipers, instead of through them."

The galleries in the calipers are such that the pistons are on a dead-end. It is impossible to "pull thru" the calipers. About the best you can do is pull the pistons "IN" removing as much fluid as possible from the calipers, then bleeding and pushing the new DOT4 back into the pistons. There is a direct connection between the bleed nipple and the brake line connection on the Brembo calipers.

I completely disassembled and cleaned my calipers after my front wheel locked up. Found crud from decomposing OEM brake lines created a "check valve" that would not allow the pressure out of the calipers. Many photos here: https://goo.gl/photos/Fhwu1x25B1eiqVPq6