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Old 07-01-2015, 07:34 AM   #1
bryantjt OP
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Rock Hard Brake Lever?

I've posted this in the FZ forums but figured I'd ask here as well.

2015 Yamaha FZ-09
1,200 miles all of which I put on from 0.0
No modifications, never had a wheel off, stock levers etc.
No wheelies, jumps, severe bumps or potholes encountered, nor has it been dropped.

Normally my brakes are a 2 finger affair for stopping, good feel, and plenty of grip to stop the bike. Over the last week it has started developing a weird issue. Any time I go over 70mph, the front brake level loses all play and is rock hard, BUT, the brakes aren't dragging and just plain don't work when I manage to squeeze the hard lever. After I cycle the lever a couple times, they work fine again.

I don't mean running 70 mph for hours on end either, I can take the bike dead cold, zip to 70 and try the brakes and its hard lever with no action. I can ride for an hour at 60-65 with no issues so it's not the pads dragging and heating up the system.

I've looked for kinked lines, overly flexible lines that might kink at speed, bled the system, pulled the calipers and cycled the pistons in and out with no sticktion, pads are in good shape, discs appear fine, discs move albeit with some effort on the floating rotor buttons.

I can duplicate the issue at will either by a quick blast to 70 or by slowly creeping up to 70 so front end rise or dive isn't the issue.

I called the dealer this morning and both he and Yamaha Technical Support are stumped so I have an appointment on Friday to bring it in and demonstrate the issue.

Any thoughts before I leave it with them?
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Old 07-01-2015, 08:00 AM   #2
LittleRedToyota
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that's bizarre.

if the brake were applying itself, i would suspect you might have water in your fluid that was expanding/turning to steam when getting hot from the brake dragging.

i'd probably still try flushing the system and putting new fluid in it.
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Old 07-01-2015, 08:02 AM   #3
bryantjt OP
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There's the key, when the lever goes hard, the brakes aren't rubbing and are a bear to actually get them to stop.
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Old 07-01-2015, 08:38 AM   #4
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I agree with LRT. Flush and change fluid is cheap, easy and if there is some debris somewhere causing the problem it might remove the debris.

Otherwise I'd look for a mechanical issue in the lever area. A pebble in some little cranny of the lever pivot area that gets vibrated up into a spot that locks it up. Something like that..... have to remove the lever to see.
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Old 07-01-2015, 08:40 AM   #5
bryantjt OP
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Lever has been removed and inspected, no issues there. I'll get some fluid on the way home and flush it out, potentially will open the Mc and inspect the plunger.
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Old 07-01-2015, 09:01 AM   #6
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I am assuming the bike has ABS. It seems that you have a problem with the front wheel speed sensor. Above 70 mph the sensor is not properly registering the teeth on the ring, and the computer thinks the wheel is locked.

If it was a hydraulic or debris problem, you'd be able to replicate it at slower speeds. Just a guess but I am an automotive engineer...
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Old 07-01-2015, 09:02 AM   #7
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No abs on the FZ, just regular old hydraulics.
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Old 07-01-2015, 09:07 AM   #8
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Does the lever move at all? Just thinking that the lever locking in its pivot or the MC piston means little to no movement. Is there mechanical slack before the piston moves normally? Is that mechanical slack there now?

If the problem is down at the wheel then brake line expansion and a little bit of master piston seal expansion could be felt.

Edit- problem only happens at speed, not at home when dinking with it, right? That suggests either heating of the problem parts or vibration. Tried simply reducing the fluid level in the reservoir?
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Gripsteruser screwed with this post 07-01-2015 at 09:11 AM Reason: only at speed - suggest fluid level
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Old 07-01-2015, 09:17 AM   #9
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Lowest bidder components. Again. Open a case on the
https://www-odi.nhtsa.dot.gov/Vehicl...nt/index.xhtml so it isn't swept under the carpet, again.
Keep good records of you dealer visits. Be persistant.
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Old 07-01-2015, 09:33 AM   #10
bryantjt OP
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Quote:
Originally Posted by Gripsteruser View Post
Does the lever move at all? Just thinking that the lever locking in its pivot or the MC piston means little to no movement. Is there mechanical slack before the piston moves normally? Is that mechanical slack there now?

If the problem is down at the wheel then brake line expansion and a little bit of master piston seal expansion could be felt.

Edit- problem only happens at speed, not at home when dinking with it, right? That suggests either heating of the problem parts or vibration. Tried simply reducing the fluid level in the reservoir?

Yes there is normally some slack in the system before the pads actuate. When the problem occurs, there is zero slack and the lever is extremely hard to squeeze while at the same time it does next to nothing for braking power. After a full squeeze or 2, the system returns to normal operation and I have slack again and all works well.

Yes problem only occurs at speed, I can not replicate it in the garage. No combination of flexing or pushing or pulling of lines or components while using the brake lever will replicate the issue.

I did bleed the system and did not add fluid back to it as it is above the low mark on the sight glass.

If it was simply overfull and the system has never been opened, why would it only show up after 1,200 miles of use?

Regarding heat, when the system malfunctions I have stopped immediately using only the rear brake and neither the rotors or calipers are much above ambient temperature. I can place a bare hand on either component.
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Old 07-01-2015, 09:40 AM   #11
bryantjt OP
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Quote:
Originally Posted by concours View Post
Lowest bidder components. Again. Open a case on the
https://www-odi.nhtsa.dot.gov/Vehicl...nt/index.xhtml so it isn't swept under the carpet, again.
Keep good records of you dealer visits. Be persistant.

Done, thanks I wasn't sure where to document the incident(s).
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Old 07-01-2015, 09:51 AM   #12
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Quote:
Originally Posted by bryantjt View Post
Yes there is normally some slack in the system before the pads actuate. When the problem occurs, there is zero slack and the lever is extremely hard to squeeze while at the same time it does next to nothing for braking power. After a full squeeze or 2, the system returns to normal operation and I have slack again and all works well.
Sounds like it's either something with the lever pivot not pivoting, or the piston is absolutely not moving. And only happening at 70 makes for exciting diagnosis.

Examine the inside of the lever mount for galling? Grease or put anti-seize where the lever and the mount run together?

Inside the MC is much harder to see. Might be something for the dealer (have to hope they are good at the job)
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Old 07-01-2015, 10:10 AM   #13
bryantjt OP
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Pivot works nice and free, no galling, corrosion or anything. I had the lever off last night.

I'm inclined to open the MC and look for junk blocking a port rather than just dump fluid through it. I'm just trying to stay non-invasive while it is under warranty so they can't say I tampered with something.
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Old 07-01-2015, 10:40 AM   #14
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I agree that you shouldn't open the system while under warranty.

It's a puzzler.

Good luck with the dealer!
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Old 07-03-2015, 02:56 PM   #15
bryantjt OP
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Figures, ride 60 miles to the dealer and neither I nor they could replicate the issue. They had nothing to go on so I asked them to flush the system. They did and the tech took another test ride and still couldn't replicate it so I took it home. 120 miles total and I tried everything, hard stops, slow stops dragging the brakes, hard acceleration, rough roads and it all acted normal.

A few notes though:
The ride in was 20 degrees cooler than when it had been acting up, 55 vs 75 degrees. The ride home however was in the low 70's so that can be ruled out.

The new fluid is crystal clear, the original fluid (1 month of use, build date 11/14) was the color of iced tea, as is the fluid in the rear reservoir. I think I will flush the rear fluid just because.

The tech put the fluid level much lower than how it left the showroom. With the bars level, I can actually see the fluid level in the sight glass, from new I could never find the fluid level since it was so high. It looks too low on the side stand but I'm running it like this as it matches with the book for fluid level.
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