Damn front brake-FZ1

[nakedape]

Kinda stuck here. After getting the front tire changed I had the lever creep back on me but only at stops. I had planned to do caliper rebuild and trust the shop so I assumed it wasn't something they did.

Symptoms: great feel and bite initially. Rolling the bike back and forth from stationary I lose the lever. All of it, right back to the grip.

Today I eliminated hung up pistons by cleaning them and working by hand. 6-8 were balky. Re-bled system including cracking the lines at the master. Again, great feel until I roll it a few feet. Then nada.

The rotors are true. Fluid is topped off. Lines are new stainless, installed before the onset of problem.

Some ideas: master over traveled at some point and tore a seal internally. This would suck because I'd need to get a replacement or rebuild. Air is trapped in the caliper, but then how to account for a firm lever while sitting still? I'm going to use the lever to bleed again, even though the miti-vac did its job at the line change. Does my res. cap need to be cracked a bit for the overnight zip tie trick to work? Truly baffled here.

I've rebuilt every bike's brakes I've owned and never couldn't get them to work. :|

 

[nakedape]

This seems like a good deal, but I hate to throw parts at shit that ain't broke. In fact, I suspect the master is ok.

http://www.ebay.com/itm/01-05-YAMAH...ER-CYLINDER-REBUILD-KIT-32-7592-/400725646233

 

[Sticka]

Sounds like a bent rotor. Are you certain that they are true?

I took my front wheel into Cycle gear for a new tire many moons ago.
When I put it back on the bike the brakes worked fine....until I rolled it forward and the bent rotor pushed the pistons back!

CG had dropped my wheel onto the tire machine and bent one of the rotors.

How do you know that your rotors are true? How did you check them?

This was the last time that someone else changed my tires...After that I bought my own tire machine!

 

[nakedape]

^^^ I spun it by eye, but I got the motion pro tool last week so I'll try taking the wheel off, checking the run out, and remounting. The tech said it would have to pretty far out to affect braking that much, but the evidence points to misalignment. Thanks!

 

[RickM]

dumb question.. but just in case; The wheel is installed in the correct direction?

 

[nakedape]

I think so. Is there an arrow pointing the way? I've talked to the tech. He's really good, but mistakes can happen, and it happened in his care.

 

[RickM]

There are arrows on the wheel spoke and on rotor itself on Yamahas I believe.

But unlikely it's wrong. It does sound more like bent rotor(s).

 

[wildwhl]

oddly, I've had the same scenario on bikes where I suspected a bent rotor or faulty master cylinder. However, on a couple of them, zip tied lever over night *fixed* the problem. Not because it removed any air in the system (in these cases) but because it made readily apparent where the leak was at a junction/banjo bolt/etc.

Hopefully I've been of no help at all.

Cheers,

WW

 

[nakedape]

oddly, I've had the same scenario on bikes where I suspected a bent rotor or faulty master cylinder. However, on a couple of them, zip tied lever over night *fixed* the problem. Not because it removed any air in the system (in these cases) but because it made readily apparent where the leak was at a junction/banjo bolt/etc.
WW

I was wondering if the zip tie trick included cracking the cover open, or will air migrate up to the master when sealed. Leaks have been ruled out. I ordered a rebuild kit for the master for $28, but I hate to be that guy throwing parts on an unknown problem.

Confirmed rotors were straight today. Wheel is on the right way.

 

[EastBayDave]

Also realize you rotor might not be bent, but the rotor "floating buttons" may be just mis-aligned. The procedure is to remove them, clean, & remount. They apparently just screw on/off...there's a tool you can buy or make one.

I'll look back where I saw it on another site & post link...

 

[wildwhl]

I was wondering if the zip tie trick included cracking the cover open, or will air migrate up to the master when sealed. Leaks have been ruled out. I ordered a rebuild kit for the master for $28, but I hate to be that guy throwing parts on an unknown problem.

Confirmed rotors were straight today. Wheel is on the right way.

There is no need to crack the cover open.

WW

 

[nakedape]

Also realize you rotor might not be bent, but the rotor "floating buttons" may be just mis-aligned. The procedure is to remove them, clean, & remount. They apparently just screw on/off...there's a tool you can buy or make one.

I'll look back where I saw it on another site & post link...

So the lever now moves back without rolling back and forth. All the way, no resistance unless I quickly pump it, then fades back. The lever has been tied back for 48 hours, no change, no leaks, bike still as a statue.

I ordered a master rebuild kit and pads. They were worn past 50% and looked a little beat up from tire mounting.

The "buttons" look good, but I know it's not naked eye stuff. The procedure I found was to put a backing bolt (with a wide face) on the back and slowly turn them a few times to center. According to the author they don't need to come off.

 

[msethhunter]

So the lever now moves back without rolling back and forth. All the way, no resistance unless I quickly pump it, then fades back. The lever has been tied back for 48 hours, no change, no leaks, bike still as a statue.

I ordered a master rebuild kit and pads. They were worn past 50% and looked a little beat up from tire mounting.

The "buttons" look good, but I know it's not naked eye stuff. The procedure I found was to put a backing bolt (with a wide face) on the back and slowly turn them a few times to center. According to the author they don't need to come off.

Sounds to me like there is a leak. Inspect the calipers when you take them off to replace the lads to make sure you didn't drag some crud through the seals doing the tire, rebuild the master, and see if that fixes it. If not, throw a seal kit in the calipers. There would be nothing left after that.

 

[dowlinginchico]

If your lever hits the grip with no resistance, and there are no leaks, it is your master cylinder. There is a little "cup" that expands and seals as the pressure increases. If teh lever hits the bars, the cup did not expand to create any sort of pressure.

Also, if this was due to a leak, one lever pulls worth of fluid would be instantly noticeable. My vote is square on the master cylinder. That little cup is what is the sole thing that creates pressure. Everything else holds it in. If everything else is holding it in (no leaks), that leaves one thing only.

 

[nakedape]

If your lever hits the grip with no resistance, and there are no leaks, it is your master cylinder. There is a little "cup" that expands and seals as the pressure increases. If teh lever hits the bars, the cup did not expand to create any sort of pressure.

Also, if this was due to a leak, one lever pulls worth of fluid would be instantly noticeable. My vote is square on the master cylinder. That little cup is what is the sole thing that creates pressure. Everything else holds it in. If everything else is holding it in (no leaks), that leaves one thing only.

Bingo! I had it all apart today and the master would not hold pressure. Pushed in the plunger and something was sticking. I suspected someone pulled the brake lever during service when the tire was off, for whatever reason.

INstalled new master kit, bled brakes and boom, done. There were flecks of aluminum in the bore and gunk. No clue how that happened. But it's fixed. Riding for 10 days without a front brake was interesting.

Next up is caliper rebuild and new pads. Coming up on ten years this is mandatory in my mind. I cleaned the pistons and checked run out to make sure it wasn't misalignment. Just the piston. Case closed. :thumbup

 

[dowlinginchico]

Glad you fixed it! And glad I came back to check. I love being right

 

[nakedape]

Glad I remembered to update. There were about 100 people across a few forums actually BETTING things that it was not the master. Only one said "I owe you a beer." Brakes are nice, I like brakes.

 

[Zerox]

Master cylinder issues will have you pulling your hair out. In AFM production classes where we had to keep the stock master cylinder, it was normal for us to get so frustrated with erratic brake performance we'd buy another one off ebay.

 

[nakedape]

Master cylinder issues will have you pulling your hair out. In AFM production classes where we had to keep the stock master cylinder, it was normal for us to get so frustrated with erratic brake performance we'd buy another one off ebay.

Some of the suggestions were helpful. I learned I could check run out with a zip tie. Everyone has their own experience with these things, but after eliminating rotor issues, caliper sticking, and bleeding, the master it was.

What pissed me off was leaving the shop thinking "this will resolve itself" and "I'll fix it when I rebuild the calipers" when I should have rolled it back in and said see you when it's fixed. All because I didn't have the recessed axle tool to take my own wheel off. Thanks Yamaha!