MNSBR: CBR1000RR Brake Problem, Suggestions? - MNSBR

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CBR1000RR Brake Problem, Suggestions? Lever goes to the bar without resistance but only after moving.

#1 User is offline   Kent Larson Icon

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Posted 12 April 2019 - 03:17 PM

I just road a 2016 CBR1000RR with a serious front brake issue.

Parked, you can pump up the brakes and get a good feeling grip and solid lever. Start moving just a few feet and try to brake again and the lever goes to the bar without any resistance at all. Pump a few times and the brakes are back with a solid feel. Roll another few feet and they are gone again but come back with a few pumps.

Brakes were bleed well. No air in lines anywhere.

I'm guessing master cylinder has a problem and would recommend to the owner to swap it out but I don't know enough about the inner workings to know what would cause the problem. Is there an internal one-way valve that is busted?

Anyone else have this issue and know the cause and resolution?

Thanks,
Kent
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#2 User is offline   Jim Icon

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Posted 12 April 2019 - 03:50 PM

Have had similar issues with trials bike brakes. Spanish hydraulics are the worst!

There is a cross-drilled hole from the reservoir into the cylinder bore. If this is rough (not properly de-burred) it can cut the seals. Pretty uncommon problem on a Japanese bike, though. Disassembly and visual inspection of the seals and bore should reveal the problem.

Assuming the master cylinder bore is not deeply gouged (but I have honed them), a new piston assembly (cup seals usually aren't available separately) will probably fix it.
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#3 User is offline   Kent Larson Icon

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Posted 12 April 2019 - 04:31 PM

Thanks Jim!
I'll see if he's interested in doing a rebuild. If not, seems a good bet that a complete swap for a new master will do the trick.
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Posted 12 April 2019 - 06:16 PM

I would also check the run out on the discs. If they are out of spec and wobble between the pads they will immediately push the pads away from the discs when moving. This will require them to be pumped each time they are used while moving yet you can get a solid lever while sitting still.

$.02
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#5 User is offline   WillMill Icon

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Posted 12 April 2019 - 06:44 PM

View Postre tired, on 12 April 2019 - 06:16 PM, said:

I would also check the run out on the discs. If they are out of spec and wobble between the pads they will immediately push the pads away from the discs when moving. This will require them to be pumped each time they are used while moving yet you can get a solid lever while sitting still.

$.02
😊


This is what I would suspect. Bent or warped rotors, or something causing the rotors to spread the pads.
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#6 User is offline   Jim Icon

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Posted 12 April 2019 - 07:03 PM

I did consider a bent rotor, but I think it would have to be really bent for the lever to go to the bar. Should be easy to see if that's the case. But it does make more sense than a Japanese master cylinder failing so soon.
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Posted 12 April 2019 - 07:21 PM

View PostJim, on 12 April 2019 - 07:03 PM, said:

I did consider a bent rotor, but I think it would have to be really bent for the lever to go to the bar. Should be easy to see if that's the case. But it does make more sense than a Japanese master cylinder failing so soon.


Just thinking out loud here, but if both rotors were bad they would really be working against the pads making for a soft lever when rolling.

Another thing I just remembered, one of the FZ07 front wheels I picked up had the disc mating surface machined out of square causing a disc wobble of several thousandths from the factory. I had a local shop dress it flat and bingo. Same symptoms tho, never could get a good solid lever till it was dressed.
Sloppy quality control.
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#8 User is offline   Jim Icon

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Posted 12 April 2019 - 08:11 PM

View Postre tired, on 12 April 2019 - 07:21 PM, said:

Another thing I just remembered, one of the FZ07 front wheels I picked up had the disc mating surface machined out of square causing a disc wobble of several thousandths from the factory.

Just curious, what's the first character of the VIN on that bike? I'm disappointed that "Japanese" vehicles are increasingly being manufactured elsewhere.

I may have posted this before, but it amazes me that Japanese quality control has historically been so superior. One of the founders of Hewlett-Packard wrote a book called The HP Way. In it, he described a joint venture HP formed with Yokogawa in Japan (called YHP). Below is the quote that I often share:

Quote

Here is a example of what YHP was able to do. We had been making printed circuit boards in various parts of the company. Our best failure rates were about four in a thousand. We thought that was pretty good -- a little less than 0.5 percent. And that was the rate we found a lot of other companies were achieving. Our Japanese unit, on the other hand, came in with a failure rate on its printed circuit boards of only ten per million. That's four hundred times better than anything we had been able to do. ...gains in quality had come from meticulous attention to detail.

...every step in the manufacturing process must be done as carefully as possible, not as quickly as possible.

I had often seen the people in our operation in YHP spend considerable time making sure that every adjustment was done as accurately as possible. The same adjustments were done at HP in Palo Alto just as quickly as possible to get them just barely within the limits specified. This came about because the people in Palo Alto were on profit sharing, and the people in Japan were not.

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Posted 12 April 2019 - 09:19 PM

View PostJim, on 12 April 2019 - 08:11 PM, said:

Just curious, what's the first character of the VIN on that bike? I'm disappointed that "Japanese" vehicles are increasingly being manufactured elsewhere.



It's "J" so Japanese not Malaysian but the wheels are probably made by vendors I imagine and who knows what their manufacturing tolerances are.
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#10 User is offline   WillMill Icon

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Posted 12 April 2019 - 09:48 PM

View PostJim, on 12 April 2019 - 07:03 PM, said:

I did consider a bent rotor, but I think it would have to be really bent for the lever to go to the bar. Should be easy to see if that's the case. But it does make more sense than a Japanese master cylinder failing so soon.


Or.... I had a friend with a KTM EXC, that had similar problems. It ended up being bad wheel bearings causing the whole wheel to move back and forth spreading the brake pads. That bike only has one caliper. I would imagine sloppy wheel bearings on a bike with two calipers would cause a significant difference.
No matter what the problem is, it should be pretty easy to diagnose by putting the front on a stand and giving the wheel a spin, or checking for loose bearings.
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#11 User is offline   Jim Icon

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Posted 13 April 2019 - 05:43 AM

I've never seen the wheel bearing thing -- that's really good to know! Now I'm super-curious what Kent finds.
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#12 User is offline   Kent Larson Icon

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Posted 14 April 2019 - 03:29 PM

Man, I feel like such a noob. Of course it's a warped rotor!

I've never had the problem in the past and didn't jump on the rotor as an issue since I didn't feel any pulse when braking but once it was brought up here, it sparked as the obvious problem.
Went back to my friend's with a front-end stand and the rotor problem was easily obviously apparent.

Thanks for the help. I'll shuffle off in shame.
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#13 User is offline   WillMill Icon

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Posted 14 April 2019 - 05:54 PM

View PostKent Larson, on 14 April 2019 - 03:29 PM, said:

Man, I feel like such a noob. Of course it's a warped rotor!

I've never had the problem in the past and didn't jump on the rotor as an issue since I didn't feel any pulse when braking but once it was brought up here, it sparked as the obvious problem.
Went back to my friend's with a front-end stand and the rotor problem was easily obviously apparent.

Thanks for the help. I'll shuffle off in shame.


Now, the question, how did the rotor become so warped?
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