Rear Brake Problem

[Donvito]

Disassembling the rear section in preparation for new tires so doing some pm while parts are accessible. Decided to bleed the rear brake so topped of the fluid in the reservoir, applied pressure to the pedal, opened the bleed valve (got the usual flow of brake fluid), closed the bleed valve and pushed down on the pedal again to bleed but no pressure at all. No fluid to the bleed.

 

Thinking there may be a plug in the supply line, I removed the hose from the reservoir to the master cylinder, inserted a funnel into the hose and poured in brake fluid but still no pressure at the pedal.

 

I guess I need to replace or rebuild the master cylinder but just wanted to get your thoughts. Brakes were working fine so just kicking myself in the ass for messing with it.

[van avery]

You might have air in the system. The Foot brake controls the back brake and one of the front brakes. There is a bleeder up by the triple tree on the right hand side of the bike. This is the high point and most likely has air up there. Good luck.

[Donvito]

When I depress the brake lever, there is no resistance whatsoever. The plunger just goes up and down. The level of fluid doesn't decrease. No fluid is evident at the bleed points including the top one by the triple tree. It seems like there is no fluid entering the chamber. I removed the piece on the master cylinder that the hose connects to and there was fluid in there. The small orifices seem clear. I don't know what else to do.

[pmelah]

When I depress the brake lever, there is no resistance whatsoever. The plunger just goes up and down. The level of fluid doesn't decrease. No fluid is evident at the bleed points including the top one by the triple tree. It seems like there is no fluid entering the chamber. I removed the piece on the master cylinder that the hose connects to and there was fluid in there. The small orifices seem clear. I don't know what else to do.

 

i had the same problem i was told to get a vacuum pump and do it that way i got the pump at Harbor freight filled the master cyl hooked the hose to the bleeder and started pumping keeping the master full until i got clean fluid on the front break and then repeated same process on back break after that i had pressure on the breaks and left it alone so you may want to try that also put some Teflon tape on the threads of each bleeder valve before you start the process it really helps getting all the air out

[frankd]

It also sounds to me like you've just got air in your system. Remember that the left front disk is also linked with the rear brake, so if the line going to it has air as suggested by Van it will cause the brake pedal to be soft or missing. You also mentioned that you couldn't see the master cylinder draw any fluid out of the reservoir.....fluid only flows into the master cylinder when it's at the relaxed position, and then only when it needs some fluid. If none is lost, it doesn't draw any, it merely re-uses what it has.

 

Next you do need to bleed the left front brake. The bleeder Van mentioned is in front of the tank cover (OK, actually the battery & air filter cover), just to the right of the center. Remove your tank cover and being careful not to spill brake fluid on anything, bleed it here. Then after you get all the air from it, check your left front calilper. Then check the rear brake caliper again. It's best to use a small, clear piece of tubing pushed over the end of the bleeder.

 

A vacuum bleeder will help, but it's not necessary on a MK II. Getting somebody (wife, son, daughter, ....) to push the brake pedal for you is almost necessary though. Just have the helper push the pedal down and NOT release it when you say "DOWN". Have them pump the brake pedal 4-5 times real quick, and then hold it down. While they are holding it down, open the bleeder in front of the tank cover. Then close the bleeder, and tell them "UP" When you open the bleeder, you will probably see air come out. Repeat this process over until you see no more air. Once you have some brake pedal, you can quit pumping the brake and only have them push it down once and hold it. Also, make sure you don't run out of brake fluid in the reservoir.

 

Sometimes air bubbles will cling to the lines and not rise to the top----not enough for you to have no pedal, but it may be a bit spongy. Sometimes you have to bleed brakes a 2nd time the next day.

[abusive throttle cranker]

You can get a piece of tubing from the hardware store- a clamp too. Run the tubing down to a container. Good way to control that fluid.

[Donvito]

Thanks for the advice. I have changed the brake fluid several times throughout the years as well as the clutch fluid and I have never had this happen.

 

The brakes were working find until I bled the rear brake caliper. I depressed the pedal with the bleeder closed, opened the bleeder and saw the normal flow of fluid. While holding the pedal down, I closed the bleeder and released the pedal. When I pushed down to bleed it again the pedal traveled to the limit with no resistance.

 

I tried bleeding the front left and the upper bleed valve and I get nothing, no fluid or air. I removed the hose going to the front brake from the master cylinder, put my fiinger over the hole and I felt nothing when I pumped the brake pedal. I also pressurized the fluid reservoir, opened the rear bleed screw and manipulated the pedal and no fluid or air came out of the bleed screw. I had a clear plastic tube attached to the bleeder with the end submerged in brake fluid while I did this.

 

 

There was no way for air to enter the system. I'm thinking it's a problem with the master cylinder but I don't know how to test it. Is there a way?

[skydoc_17]

Hey Don,

At the rear of the Rear master Cylinder, there is the Proportioning Valve. This spring loaded control valve will get an air bubble trapped in it and will basically keep fluid from going to the rear caliper. I suggest that you remove this valve, and remove all of the inner parts, then reinstall the housing. I think you will find that your rear caliper will function properly after that. With that valve being at the highest point of the rear of the braking system, it is prone to getting an air bubble in it that is "pesky" to remove.

If you are interested in changing your braking system to a more conventional system, and removing the Proportioning valve completely, check out this link:

http://www.venturerider.org/classifieds/showproduct.php?product=3878&title=first-gens-sbrake-line-delink-kit-21&cat=22

 

The rear master cylinder as a complete unit is no longer offered from Yamaha, but the rebuild kit is still available. Considering that you got 26 years of service out of that rear master cylinder, a rebuild every quarter century doesn't sound like a bad deal to me.

As with many items on a First Gen., patience, and a few good tools will make the job easier.

Earl

[ctraylor]

Disassembling the rear section in preparation for new tires so doing some pm while parts are accessible. Decided to bleed the rear brake so topped of the fluid in the reservoir, applied pressure to the pedal, opened the bleed valve (got the usual flow of brake fluid), closed the bleed valve and pushed down on the pedal again to bleed but no pressure at all. No fluid to the bleed.

 

Thinking there may be a plug in the supply line, I removed the hose from the reservoir to the master cylinder, inserted a funnel into the hose and poured in brake fluid but still no pressure at the pedal.

 

I guess I need to replace or rebuild the master cylinder but just wanted to get your thoughts. Brakes were working fine so just kicking myself in the ass for messing with it.

Sounds like the piston is stuck in. Sometimes when you push in the piston past the normal travel there can be rust on the walls and cause the piston to stick. I always make it a habit not to push the piston in too far for that reasonl

[Donvito]

Sounds like the piston is stuck in. Sometimes when you push in the piston past the normal travel there can be rust on the walls and cause the piston to stick. I always make it a habit not to push the piston in too far for that reasonl

 

If that's the case, how do I free the piston?

[Snaggletooth]

You can disconnect the union bolt at the caliper and use air pressure to blow the pistons out. I only do that when I split the caliper body.

 

Contain the piston with a rag. They can move right along when they come out.

[Donvito]

Not sure I understand. You are saying the piston in the mc may be stuck. To free it I can apply air pressure at the caliper which would mean pushing air pressure back through the hose connecting the mc to the rear caliper. If this is correct, how do I attach the air hose to the brake hose?

 

Also, does anyone have a picture of the internal parts of the mc or rebuild instructions for the mc with pictures? Thanks.

[Donvito]

Hey Don,

At the rear of the Rear master Cylinder, there is the Proportioning Valve. This spring loaded control valve will get an air bubble trapped in it and will basically keep fluid from going to the rear caliper. I suggest that you remove this valve, and remove all of the inner parts, then reinstall the housing. I think you will find that your rear caliper will function properly after that. With that valve being at the highest point of the rear of the braking system, it is prone to getting an air bubble in it that is "pesky" to remove.

If you are interested in changing your braking system to a more conventional system, and removing the Proportioning valve completely, check out this link:

http://www.venturerider.org/classifieds/showproduct.php?product=3878&title=first-gens-sbrake-line-delink-kit-21&cat=22

 

The rear master cylinder as a complete unit is no longer offered from Yamaha, but the rebuild kit is still available. Considering that you got 26 years of service out of that rear master cylinder, a rebuild every quarter century doesn't sound like a bad deal to me.

As with many items on a First Gen., patience, and a few good tools will make the job easier.

Earl

 

How do I remove the proportioning valve? Are you saying to remove the inner parts and reinstall the housing? Can you elaborate on your instructions. Thanks.

[Snaggletooth]

Not sure I understand. You are saying the piston in the mc may be stuck. .

 

Sorry on that one. I didn't read back far enough to catch up. I was talking about the piston in the brake caliper, not the MC.

 

I'm looking for some pic of the proportioning valve and internal assmebly.

[Snaggletooth]

Here are a couple threads discussing the proportioning valve.

 

There are no breakdowns or rebuild kits. New valves are, or were still available when I last checked for about $175 bucks I think.

 

http://www.venturerider.org/forum/showthread.php?t=69867&highlight=proportioning+valve

 

http://www.venturerider.org/forum/showthread.php?t=66186&highlight=proportioning+valve

 

 

[oldandcrotchety]

Hey Don,

 

 

The rear master cylinder as a complete unit is no longer offered from Yamaha, but the rebuild kit is still available. Considering that you got 26 years of service out of that rear master cylinder, a rebuild every quarter century doesn't sound like a bad deal to me.

As with many items on a First Gen., patience, and a few good tools will make the job easier.

Earl

 

You can still get the complete master cylinder from "Flat Out Motorcycles" in Indianapolis for $193.53 (part # 3JT-2583V-00-00 (replaces 1NL-25850-50-00).

[Yammer Dan]

I took my proportioning valve apart cleaned it carefully and put it back togather a couple years ago. Still going.

[Donvito]

I took my proportioning valve apart cleaned it carefully and put it back togather a couple years ago. Still going.

 

Why did you take it apart and clean it? Was it causing a problem with your braking system and how did you know it was the cause?

 

I believe some folks have removed the proportioning valve or at least removed the interior parts. If you have, how did it affect braking? Do you recommend doing that? Thanks.

[Prairiehammer]

Why did you take it apart and clean it? Was it causing a problem with your braking system and how did you know it was the cause?

 

I believe some folks have removed the proportioning valve or at least removed the interior parts. If you have, how did it affect braking? Do you recommend doing that? Thanks.

A couple summers ago, I had the issue of no rear brake. Bleeding, bleeding, bleeding did nothing. I tried all the tricks: reverse bleed (pump fluid from the rear caliper bleed screw into the rear reservoir); weighting the brake pedal down and waiting overnight; bleeding at the triple tree; bleeding, bleeding the front; cracking the banjo bolt at the metering valve, ad nauseum. I had that proportioning valve apart several times; tried different configurations to assembling the proportioning valve; obtained a rebuilt/refurbished FJ1300 rear caliper from Skydoc; rebuilt the rear master cylinder with a new kit. Nothing seemed to work for long.

Finally, I gutted the proportioning valve and after some more bleeding (there is a large void in the proportioning valve that must be filled with fluid) I had a reliable rear brake. I have noticed no adverse effects from having no functioning proportioning valve. My rear brake is still linked to the left front.

[Snaggletooth]

When the valve works correctly it provide 70% pressure to the left front brake and 30% pressure to the rear. As you apply pressure to the foot brake the valve begings to open slowing applying pressure to the rear brake first then opening more to allow flow to the front left side until it it hits the 70/30 split.

 

If you remove the spool valve from the inside of the proportioning valve you end up with a 50/50 split on pressure. Workable..... sure. I rode mine like that for about a year until I got the parts I needed to make the valve work correctly.

 

Why take it apart? When there is a fluid flow problem the proportioning valve is suspect due to the internal porting and the moving parts inside. Sometimes ya gotta look to be sure.

[Prairiehammer]

Sometimes ya gotta look to be sure.

Yeah, I looked inside at the proportioning valve and it LOOKED BRAND NEW with no apparent issues.

Edited June 12, 2013 by Prairiehammer

[Snaggletooth]

Looking don't always help either. The rear brakes on mine when I bought it were pretty much in a state of chaos. The POs son had removed a lot of parts to rebuild and left them in a box in pieces.

 

The proportioning valve and been opened and parts removed. The parts looked fine but with no breakdown and or kits available there was a general lack of information on how it was supposed to go back together. Took a bit of experimenting and a few parts from another valve to get it to work the way it was supposed to.

 

There is only one way that spool valve and cup will work, but a couple of ways it will go together.

 

As long as you're the first one in you're golden. An unknown attempt before you and it's time.

[Prairiehammer]

Workable..... sure.

I was not able to lock up the rear brake on a gravel road after removing the proportioning valve spool, so I decided it was good. One mitigating factor may have been the "progressive" (Skydoc's term) FJ1300 rear caliper. It has un-equal sized pistons, that Earl says activate progressively, instead of all at once.

Also, I retained the stock organic rear brake pads, but installed sintered (SBS, equal to EBC HH) brake pads on the front.

 

 

I rode mine like that for about a year until I got the parts I needed to make the valve work correctly.

 

Since the proportioning valve or its internal parts are not called out with separate part numbers, how did you find, and what parts did you use to make it work correctly?

[Snaggletooth]

 

Since the proportioning valve or its internal parts are not called out with separate part numbers, how did you find, and what parts did you use to make it work correctly?

 

 

A lot of experimenting in the beginning. I think I had the valve off 5 or 6 times trying different stuff.

 

Then a member from the Ventureres actually took his working valve off his bike and broke it down to see what was in there and how it went in. Then I knew what I needed and how to reassmeble it. Without his help it would probably still be a "no spool" setup. Or bypassed to split by now.

 

I had pics on file of everything I found but they were on my old hardrive when it crashed. No backups. D'oh!

[Yammer Dan]

Why did you take it apart and clean it? Was it causing a problem with your braking system and how did you know it was the cause?

 

I believe some folks have removed the proportioning valve or at least removed the interior parts. If you have, how did it affect braking? Do you recommend doing that? Thanks.

 

Couldn't get solid enough brake to suite me, I love the linked system and ain't gonna change it. Found a set of braided brake lines ( all 5 lines 192 bucks) and have a set of calipers ready to go but don't see need to get in a hurry. My brakes work fine.