Front brake bleeding... pulling my hair out. - SV1000 Portal
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post #1 of 25 (permalink) Old 3rd August 2013, 02:16 AM Thread Starter
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Front brake bleeding... pulling my hair out.

I'm using the stock SV1000S master cylinder with 2006/7 GSX-R750 radial calipers. I think the Gixxer master cylinder has a bleeder valve just like the calipers, but the SV piece does not. Therefore, I don't know how to bleed the master cylinder itself.

I had no difficulties the last time I changed brake fluid. It took a while, but bleeding at each caliper nipple eventually resulted in a very firm lever. NOT THIS TIME!! I've been at this ALL DAY, hours and hours, and the lever still pulls all the way back to the bar with very little resistance. The bubbles disappeared from the calipers hours ago, so if there is still air in the system, it's hiding somewhere else. I've gone through an entire large bottle of brake fluid.

I bought a small syringe to attempt "reverse" bleeding by pumping fluid into the caliper nipples-- many riders swear by this method-- but I can't figure it out. No matter how I try, there is always a bit of air just ahead of the fluid in the syringe... which will be pumped straight into the caliper. Makes no sense.

I tried a hand-held Mity Vac, which also had zero effect. I've never had any luck with the Mity Vac in the past, though. Guys brag about swapping their brake fluid in five minutes with these things and I don't see how that is remotely possible. Generally the only thing the Mity Vac does for me is make a mess.

For a few hours I tried gravity-bleeding while I did some other work, which also had zero effect. I've flicked and shaken the lines and tapped the calipers with a mallet. Right now I have the lever zip-tied to the clip-on. I'll check it again in the morning, but I don't expect any change.

I rebuilt the master cylinder and both calipers yesterday; brand new seals and such simple operation that I can't imagine what I could've messed up. There are no leaks anywhere in the system.

Ideas?
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post #2 of 25 (permalink) Old 3rd August 2013, 02:41 AM
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Have you tried squeezing the lever repetitively say 40-50 times in rapid succession? usually builds the pressure otherwise go back to bleeding.


Easiest way is to put your hose on the nipple, put the syringe into the hose and add a little brake fluid, tape the shit out of the hose until you can see it is full and no air, fill the syringe with fluid, put the plunger in, open the nipple, pull the lever and push the bastard through, stop when the syringe is out of fluid,
Tighten up the nipple then let go of the lever,
Carefully pull out the syringe and hold the hose, pull the plunger back out and rinse and repeat, As easy as that.

Took me all of 15mins to replace my front brake lines with braided lines and to bleed to the callipers and drain the master and push a couple of cycles of new fluid through the system,
Pays to have a second syringe that you can use to suck out the fluid from the res when it fills up.
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post #3 of 25 (permalink) Old 3rd August 2013, 07:17 AM
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Try bleeding air from the top of the system by cracking open the line where it meets the MC at the handlebars. Follow the same procedure as if you were bleeding from the nipple at the caliper end (prebuild pressure at the lever etc.). This will help rid the system of the air that has floated to the top of the lines. Whilst doing this, have the bike on the side stand and angle the bars so that the banjo nut is as high as possible compared to the MC etc.

Let us know how you get on.....


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post #4 of 25 (permalink) Old 3rd August 2013, 07:46 AM
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Had a similar situation with a Gsxr a few years ago. Solved by pressing calipers pistons all the way home and wedging pads with small wooden wedges.
Don't known if that's your issue, but worth a try.
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post #5 of 25 (permalink) Old 3rd August 2013, 10:53 AM
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Quote:
Originally Posted by Triple View Post
I rebuilt the master cylinder and both calipers yesterday;
I think this is the key bit of information, the system would have been dry and needs priming. I went through this recently when I changed over to Hel lines. What worked for me was using one of those easy bleed lines, with the one way valve in the end, and this is how I did it. I used a box to sit a plastic wash basin and put my bleed bottle in it, just in case I knocked it over. This also gave a good bit of vertical bleed hose coming off the bleed nipple. By pumping the lever the brake fluid built up in the hose, but got more in by holding this hose upright, i.e. I took it out of the bottle. By letting the brake lever out with the bleed nipple open, the effectively reverse bled the system under gravity, I could see the bubbles coming out at the master cylinder. After doing that a few times, I tried bleeding it as normal. Pumping up the system with the bleed nipple closed, holding the lever in, then opening the bleed nipple, closing it, and repeating this procedure. It took a little while, but I didn't use anywhere near the amount of fluid you've unfortunately went through.
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post #6 of 25 (permalink) Old 3rd August 2013, 12:41 PM
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Quote:
Originally Posted by Triple View Post
I bought a small syringe to attempt "reverse" bleeding by pumping fluid into the caliper nipples

Ideas?
You need a BIG syringe it will work.
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post #7 of 25 (permalink) Old 3rd August 2013, 04:35 PM Thread Starter
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Quote:
Originally Posted by t20p1 View Post
You need a BIG syringe it will work.
I would still be pumping air into calipers that have already long-since been bled. The more I read about this method, the more it sounds like a good way to fill an empty system, not finish a system that is already mostly airless. I get good, bubble-free flow from both caliper bleeders.

The air must be trapped in the master cylinder. I hate to bleed at the banjo bolt, but I don't think I have much choice. Not good for the soft copper crush washers and bound to make a hell of a mess.
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post #8 of 25 (permalink) Old 3rd August 2013, 04:50 PM
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Try the 'zip-tie' method... I can't explain why, but it helped bleed the brakes on one of my bikes (maybe just leaving the bike alone overnight would too). Before I tried that I was going with the 'regular' method for over 3 hours to no avail...

D.

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Last edited by danci1973; 3rd August 2013 at 04:54 PM.
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post #9 of 25 (permalink) Old 3rd August 2013, 07:29 PM Thread Starter
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Quote:
Originally Posted by Triple View Post
The air must be trapped in the master cylinder. I hate to bleed at the banjo bolt, but I don't think I have much choice. Not good for the soft copper crush washers and bound to make a hell of a mess.
Tried this. No visible bubbles from around the washers, but it's hard to tell without a real bleeder screw and some clear hose. Still, I ran an entire reservoir of fluid this way and NO CHANGE in resistance at the lever.

Quote:
Originally Posted by danci1973 View Post
Try the 'zip-tie' method... I can't explain why, but it helped bleed the brakes on one of my bikes (maybe just leaving the bike alone overnight would too). Before I tried that I was going with the 'regular' method for over 3 hours to no avail...
I zip-tied the lever to the bar last night and there was no difference this morning.

I just spent the last two hours trying this method:

Brake bleeding problems? Look here, fail proof bleeding

No change in resistance at the lever.

I unbolted the master cylinder and lever from the bar and tried squeezing the brake from different positions, particularly with the banjo bolt lower than the lever (since the mounted angle of the assembly puts the fitting above the lever, a high spot that could hold a bubble). No change in resistance at the lever.

I'm completely baffled. If it was the master cylinder, I would expect one of two (or both) symptoms: leaking fluid or little to no resistance on the lever. There are no leaks anywhere and there is pressure at the lever, just not enough. Plus, I just rebuilt the master cylinder!

I've bled the brakes on dozens of different vehicles over the years, car and motorcycle, including this exact same bike with this exact same set-up, and I've never run into anything like this.
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post #10 of 25 (permalink) Old 3rd August 2013, 08:55 PM
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Sounds to me like you're not building pressure up to hose when you're squeezing the lever. I would check the inner oring, piston and cup setting. One of those is scratched, faulty or damaged during the refurb.
You can't be going through that many bottles of fluid without actually got rid of all the air in the line.


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post #11 of 25 (permalink) Old 4th August 2013, 03:56 AM Thread Starter
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The master cylinder is such a simple mechanism, I can't imagine what could have been damaged upon reassembly, especially with all new seals. Still, I can't imagine what else the problem could be, so I will remove and disassemble it in the morning.

Perhaps worth mentioning is the reason for doing all this in the first place. I was originally getting some serious drag on the brakes; trying to spin the wheel with everything I had would only get me about 1/4 rotation. Feel at the lever was fine and I suspected it may have been the crappy OEM rubber lines. I've had the inner linings on rubber automotive lines fail several times, which can prevent the release of pressure from the calipers and cause drag or even lock-up.

I replaced the rubber with braided steel lines but wanted to rule out everything else just in case. Rebuilt the master cylinder and both calipers; the calipers were gunky on the outside but both pieces looked squeaky-clean on the inside... no visible scratches or contaminated fluid and the original seals looked as good as the new ones.

NOW... even with the lack of pressure at the brake lever, the calipers are still dragging on the rotors exactly as before. Meaning, even when I'm not engaging the brake lever at all, in an already squishy system, the front wheel barely spins by hand.
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post #12 of 25 (permalink) Old 4th August 2013, 04:34 AM
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Front brake bleeding... pulling my hair out.

It sounds to me like a seal on the master piston or the one at front of it is in backwards or some thing similar.
-ms


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post #13 of 25 (permalink) Old 4th August 2013, 10:08 AM
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Have you cleaned the bobbins on the rotors?
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post #14 of 25 (permalink) Old 4th August 2013, 08:27 PM Thread Starter
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I removed the calipers one at a time, pressed out the pistons, and tried to bleed out any stuck air while compressing them back in, but there wasn't any. I'm convinced the air was bled completely out of the calipers days ago.

I removed and disassembled the master cylinder. Everything was in its correct order, the seals were pointed in their correct directions, the parts exactly matched the old ones I replaced, and nothing was damaged. Movement of the spring and piston was buttery smooth upon reassembly.

I tried "bench bleeding," but the procedure I found online didn't make much sense. Basically, with the lever and reservoir reattached, I held my thumb over the outlet to squeeze air out and allow fluid to be drawn in. However, this seal obviously has to be broken to reinstall the line, so some air was drawn back in.

Tried bleeding it the old way and Moto_Joe's way again, tried a little of both at the same time, tried the Mity Vac... blah blah blah. I'm right back where I started with exactly the same pressure at the lever and no bubbles leaving the calipers.

This seems to narrow the problem to the calipers themselves now, but I would just about bet my life that they will look fine upon disassembly. This is the most bizarre brake job I've ever done.

I'm leaning towards one of two "possibilities" :

1) I've somehow developed superhuman strength, allowing me to easily pull the lever back to the bar despite an airless brake system, or

2) My garage has slipped into another dimension that doesn't abide by our accepted laws of physics.

What is ESPECIALLY awesome is that I'm supposed to be leaving on a 1500-mile road trip Wednesday morning.
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post #15 of 25 (permalink) Old 5th August 2013, 12:33 AM
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I had a problem recently with bleeding my front calipers, I tried everything like removing the calipers, moving them around, knocking them with a mallet to release any bubbles, zip-tying down the lever overnight, opening and bleeding the banjo bolt by the master etc. etc. I still had a brake lever that I could pull all the way in easily.

The only way I solved it was fitting speed bleeders, I ordered them on next day delivery. Fitted them in about 5 minutes, bled the system again and it was much better. The lever still pulls in further than before but I've got adjustable levers and moved them out, braking is fine and hard now. I think the problem was that the clear tube I had over the bleed nipple wasn't tight enough and let air back in every time I tried bleeding, with the speed bleeders that can't happen.

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