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Old 08-05-2017, 01:23 AM   #1
Turtleface
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Consistent brake lever fade

So, I've run into an interesting problem with the front brakes on my '07 ZX6R.

The issue:
Front brake lever becomes soft and spongy over a period of two-three days. It's a fairly progressive degradation of lever feel. At the end of the two-three day period, I can pull the lever to the bar. Brakes still engage, but without much bite.

Things I've done:
Brake lines were upgraded ~3000 miles ago to stainless. Zero issues, prior to this one. Bleeding the entire system, per the factory manual, gives a great lever feel. Bleeding just the master cylinder, achieves the same result. Bike was involved in a low speed crash about two and a half months ago. No obvious damage to any components, all known damage is cosmetic, and on the left side of the bike.

No leaks that I can see. Rotors are within spec for thickness, but I don't have the equipment to check runout. No odd feelings under heavy braking. Calipers and pistons don't appear to be seized. Anyone have any insight as to how this is happening?
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Old 08-05-2017, 04:38 AM   #2
MaxGs
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Quote:
Originally Posted by Turtleface View Post
So, I've run into an interesting problem with the front brakes on my '07 ZX6R.

The issue:
Front brake lever becomes soft and spongy over a period of two-three days. It's a fairly progressive degradation of lever feel. At the end of the two-three day period, I can pull the lever to the bar. Brakes still engage, but without much bite.

Things I've done:
Brake lines were upgraded ~3000 miles ago to stainless. Zero issues, prior to this one. Bleeding the entire system, per the factory manual, gives a great lever feel. Bleeding just the master cylinder, achieves the same result. Bike was involved in a low speed crash about two and a half months ago. No obvious damage to any components, all known damage is cosmetic, and on the left side of the bike.

No leaks that I can see. Rotors are within spec for thickness, but I don't have the equipment to check runout. No odd feelings under heavy braking. Calipers and pistons don't appear to be seized. Anyone have any insight as to how this is happening?
The Occam's razor principal would say its related to the stainless lines. Air is getting in somewhere.

Did you use new crush washers?
Are the bleeders torqued correctly?
Are the banjo bolts torqued correctly?
Visually inspecting the lines, is there any damage?
Is there any fluid weeping?

Since the air is getting in over 2 or 3 days, the leak is very small.

If retorqueing everything doesn't work, i'd start over and replace all the crush washers. I'd also consider replacing all the bleeders.

Other less likely causes...

Stainless line fitting leaking
Bad seals in the brake calipers

A few days back a ran across an article about installing stainless lines on my Flipboard app from Motorcycles.com. It's worth a quick read: http://flip.it/b8RbYL

On the crush washers...
"Always replace the crush washers when the banjo bolts have been removed. The soft copper (for steel banjos) or aluminum (for aluminum banjos) is designed to conform to any irregularities on the fitting or mounting surface. A washer should be used on both sides of the banjo. If two banjos are being bolted together (as on the front brake master cylinder), be sure to use a crush washer between the two banjos, as well. Screw the banjo bolts in finger tight and check your hose routing before you torque things down. You donít want any sharp bends or kinks in the lines. If things donít line up right you may have the banjos at the wrong mounting point. Hydraulic line manufacturers spend a lot of time making sure that the fittings have the same bend as the OE lines they replace. If something doesnít look right, it probably isnít."
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Old 08-06-2017, 08:49 PM   #3
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Thanks for the insight, Max! In regards to the brake lines, all washers were replaced, and banjo bolts torqued to specs. As a habit, I torque everything to spec, if one is available. If not, I use the generic size/torque chart in my manual.

I think the biggest issue I'm having is with the work done by the previous owner's mechanics. It's astounding how many bolts I've found INCREDIBLY over-tight, when the previous work was done by supposedly reputable shops. Torque wrench? What's that? The calipers pistons move in a subpar fashion, and brake dust was gunked all over everything.

Closer inspection reveals incredibly minor weeping around the bleeders on the left caliper, and at the master. No damage to lines. No damage to any brake components, in regards to my little crash. I've re-wrapped the threads on the nipple with teflon tape, and torqued them to spec, still see a tiny, tiny amount of fluid around the base of the bleeders, and the interior on the nipple itself. I'm under the assumption that if torqued to tightly, the tips on the ends of the bleeders would deform prior to the caliper body, and potentially cause leaks. Which is where I THINK my problem lies.

Regardless, I've been sourcing front brake components for a minute now. Have take off rotors, as I'm confident that my right front is at least a little warped. When I was trying to pull the pad pins out of the right caliper, to clean the pistons and what have you, I ended up stripping a pad retainer pin. Attempt to use and EZ-out, and following that failure, drilling the pin resulted in damage beyond economical repair. So, I picked up a pair of calipers off eBay. Broke them down, cleaned them up. Also picked up a set of seals for both calipers, genuine Kawasaki parts, and cheap, from a member on a forum I frequent. New EBC HH pads are ready to be installed. New crush washers sourced for the lines. Only things I haven't acquired are the seals and piston body for the master cylinder. Will be ordering those on Friday.

So, I think I'll end up solving my brake issues, in the end. But I'd like to figure out the cause of my problem still, so I can more quickly diagnose problems in the future.
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Old 08-06-2017, 09:32 PM   #4
MaxGs
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New calipers.... no more bleeder problem !!

Thank for eBay.

Good luck with the repairs.

NW meet 6:30 tomorrow (monday) night at Chuy's near 1960 and 290. Try to make it.
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Old 08-06-2017, 09:55 PM   #5
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Quote:
Originally Posted by Turtleface View Post
Thanks for the insight, Max! In regards to the brake lines, all washers were replaced, and banjo bolts torqued to specs. As a habit, I torque everything to spec, if one is available. If not, I use the generic size/torque chart in my manual.

I think the biggest issue I'm having is with the work done by the previous owner's mechanics. It's astounding how many bolts I've found INCREDIBLY over-tight, when the previous work was done by supposedly reputable shops. Torque wrench? What's that? The calipers pistons move in a subpar fashion, and brake dust was gunked all over everything.

Closer inspection reveals incredibly minor weeping around the bleeders on the left caliper, and at the master. No damage to lines. No damage to any brake components, in regards to my little crash. I've re-wrapped the threads on the nipple with teflon tape, and torqued them to spec, still see a tiny, tiny amount of fluid around the base of the bleeders, and the interior on the nipple itself. I'm under the assumption that if torqued to tightly, the tips on the ends of the bleeders would deform prior to the caliper body, and potentially cause leaks. Which is where I THINK my problem lies.

Regardless, I've been sourcing front brake components for a minute now. Have take off rotors, as I'm confident that my right front is at least a little warped. When I was trying to pull the pad pins out of the right caliper, to clean the pistons and what have you, I ended up stripping a pad retainer pin. Attempt to use and EZ-out, and following that failure, drilling the pin resulted in damage beyond economical repair. So, I picked up a pair of calipers off eBay. Broke them down, cleaned them up. Also picked up a set of seals for both calipers, genuine Kawasaki parts, and cheap, from a member on a forum I frequent. New EBC HH pads are ready to be installed. New crush washers sourced for the lines. Only things I haven't acquired are the seals and piston body for the master cylinder. Will be ordering those on Friday.

So, I think I'll end up solving my brake issues, in the end. But I'd like to figure out the cause of my problem still, so I can more quickly diagnose problems in the future.
I am assuming you picked up said components off ZX6R.com? Glad to hear you got everything sorted, the brakes on that gen zx6 are $$. Maybe consider a brembo MC if replacing oem, either way you can't go wrong!
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Old 08-06-2017, 09:56 PM   #6
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If I wasn't in Pearland, I'd probably show up. As it is, my tires are pretty much at the end of their life, and my brakes are kinda iffy at best. I know it's a meetup and not a hard ride, but this is my daily, so I have beg off. Once things are sorted, and I'm comfortable with how my bike handles once important suspension bits are sorted, I definelty plan on being on the next Morstang ride following completion of repairs.
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Old 08-06-2017, 10:02 PM   #7
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Quote:
Originally Posted by Schooley View Post
I am assuming you picked up said components off ZX6R.com? Glad to hear you got everything sorted, the brakes on that gen zx6 are $$. Maybe consider a brembo MC if replacing oem, either way you can't go wrong!
Yes sir. Rotors and seals came from a few good folks I'll callout when I finally get everything back together. I'm not replacing the master, per say, just the internals, minus the actual MC body. ~$50 dollars, with all seals, and shipping. I've considered a Brembo, but can't justify it for my needs/skill level. My goal is to get the front brakes and suspension back to stock, adjusted for my weight and riding style. After I learn how to control that setup to it's full potential, I'll more seriously weigh the higher dollar upgrades. Reckon I've got years before I'm there, so that's just more time to save up for the good stuff!

As an aside, I haven't got anything sorted yet. Except for parts acquisition. I ride the bike to work everyday, all of 10 miles, round trip. The fade is progressive enough that I can just re-bleed the master before it's too dangerous. Literally, I can do it in less time than it takes me to get my gear on.

Last edited by Turtleface; 08-06-2017 at 10:05 PM.
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