Front brake frustration

[Mad Dog]

Ok... I put in new front brake pads and rebuilt the front master cylinder, which had a small drip developing. Now I have no front brake... It was fine before.

So.. is there an anti-dive system on a 2006 RSV? I can't see one if it is linked into the brake system, looks like a straight shot with just the tee to split the lines between the rotors.

I have had the master cylinder apart a half dozen times and I am convinced that it is assembled correctly, the rubber seals are snug in the bore.. like the old one were. The middle cup washer is facing inboard just like the old one was, and there is no scoring in the bore. Both holes in the bottom of the reservoir are open and clean. Pushing the calipers open by hand pushed fluid back into the reservoir, pumping the lever moves the calipers back against the rotor but then there is no force/pressure to force the pads tight.

We have bled and rebled. Bled the normal way, and bled with a vacuum pump. We have done right side first and left side first. I tied the lever back, tapped the lines, let it sit overnight ... for two nights ... nothing changed. We did the chicken bone dance. I had two more guys here last night, one is a mechanic, for three hours ... nothing.

 

So... what to do...?

Is it probable that the master cylander rebuild kit is defective? or is there an anti-dive I am missing (I dont see it mentioned in the manual)

Any help would be appreciated, we are going on day four of this crap.

Edited May 19, 2015 by Mad Dog
spelling

[Great White]

Keep in mind it's difficult to troubleshoot these things across the internet, but your description seems to indicate a master cylinder that bypasses when pressure is applied.

 

This is typically worn seals or bores. BUt since you say you had it apart and if it was fine before, anything you changed is suspect. The seals may be installed wrong, or they may have a small nick or the kit may be manufactured incorrectly.

 

If you elect to tear it apart again, I would recommend you get the seal kit from Yamaha.

 

Anti dive was a 80's attempt at preventing dive under braking and it was, for the most part, unsuccessful. By the 90's it was gone off pretty much everything so I would be very surprised if your 2006 has one. If you only see three lines and a splitter, it does not.

 

That's about all I can do for you over the internet.

 

Good luck and I hope you find the problem.

Edited May 19, 2015 by Great White

[Mad Dog]

It does sound like bad seals, and if anyone would end up with a defective rebuild kit it would most certainly be me....

[Great White]

The only other thing I could add is bleeding. But air in the line will typically make a soft level that can be pulled to the grip. It should still build pressure, unless there's a HUGE slug of air in the line.

 

I usually reverse pressure bleed the system when it's been completely apart. This is a simple mason jar with a line and schrader brazed into the lid. I fill the jar with fresh fluid, connect the line to the caliper bleed port and then add a little pressure to the jar (very little, usually a pound or less, it is only a glass mason jar after all). This pushes the fluid up to the master as air wants to go up, not down. Works fast and easy. There are retail ready built bleeders out there for purchase that do the same job.

 

I've also "bench bled" master cylinders when that's all we've had apart. I've got a banjo bolt fitting off an old brake like with a nipple brazed on and some clear tubing. I loop it back to the master and bleed the air out of the master, just like you would with a larger automotive master cylinder. A quick reverse pressure bleed, then a quick bleed of the calipers and you're ready to go.

 

Sounds like a longer process than a vacuum bleed, but it's not. It's quick and it works first time, every time. No fooling around and that's where you save the time.

 

[etcswjoe]

i just went through the same thing and if you put the seals on as shown in the parts diagram you probally did not put them in correctly. Make sure the seals look just like the old one and when you bleed them make sure the bike is upright.

[Mad Dog]

i just went through the same thing and if you put the seals on as shown in the parts diagram you probally did not put them in correctly. Make sure the seals look just like the old one and when you bleed them make sure the bike is upright.

I saw that! The diagram shows that cupped seal on the end of the shaft! Thats crazy... but I did catch that and I put it in the middle where the old one was. Thanks!

[etcswjoe]

Even with speed bleeders it took a good half an hour of pumping to clear all the air.

[Condor]

I saw that! The diagram shows that cupped seal on the end of the shaft! Thats crazy... but I did catch that and I put it in the middle where the old one was. Thanks!

 

Even with speed bleeders it took a good half an hour of pumping to clear all the air.

 

I've been following this thread and trying to make sense of it all.... even the reverse bleed which isn't that big of a deal. On the position of the cup on the plunger, the lip should rest between the expansion hole and the larger supply hole at the floor of the reserve. Not sure where you have it now, but in the middle of the those large threads on the plunger doesn't seem to ring a bell. When a system is empty it's a PITA getting fluid to start thru the line. I'll send you a write-up on a simple method to reverse bleed. Also when using speed bleeders, DO NOT, try to pump up the pressure and seat the pads. Leave the pistons pressed back into the caliper. It reduces the volume of the caliper and takes less fluid to force the air out.... Basically initially reverse bleed the caliper, then re-install the speed bleeder, then start pumping the master to force fluid back down thru the caliper with the speed bleeder open. When the fluid is air free, close the bleeder down and seat the pads.

[cowpuc]

Another thought, may try bleeding just the master first. Cover your bike so you get no brake fluid in places it should not be, unhook the line at the master, hold your finger over the bolt hole for the bango, see if you can get pressure on just the master by bleeding around your finger. May sound corny but those masters can be finicky on a fresh rebuild bleed..

 

Also, on final bleed, sometimes ya just gotta be persistent with gentle slow movement on the lever and watch for tiny bubbles.. Even those innocent tiny little, assumingly non-problematic, almost invisable little bubbles can cause a LOT of problems in a hydraulic system..

[van avery]

have you checked to make sure the rotor is not warped. I had the same problem on an 83 wing finally found that the rotor was warped like a bowl. This caused too much travel for the calipers t travel . Here are some pictures of what I found.

[Prairiehammer]

Here is the proper orientation of the master cylinder piston and seals. The pic shows the orientation for the rear brake on a First Gen, but the same basic orientation is the same on all master cylinders.

[V7Goose]

It is fairly easy to put in the front pads with one of them not quite fully seated on the rails (with the ear on the end hanging up outside the rail it is supposed to slide on).

Goose

[Mad Dog]

Here is the proper orientation of the master cylinder piston and seals. The pic shows the orientation for the rear brake on a First Gen, but the same basic orientation is the same on all master cylinders.

[ATTACH=CONFIG]99433[/ATTACH]

 

Yup... this is exactly what I have....

[Mad Dog]

Wow, there is some great advice here. The thing is that my brakes were fine before I changed the pads and rebilt the master cylinder. Just a bit of a rubbing squeal so I figured the pads needed changing, and a one time drip from the master cylinder - so I rebuilt that. I didn't have time to look at it last night, and tonight is cut the lawn night... so hopefully I'll have time to try a thing or two like the reverse bleed.

 

Thanks again all!