Rear Brakes Locking Up

[jdross440]

My rear brakes have recently started locking up. It first happened on a recent short ride (15 miles). I noticed a brake smell and noticed it was taking more throttle. Also the brake peddle had almost no movement. When I pulled into a station they were almost totally locked and smoking. I loosened the banjo bolt at the caliper and relieved the pressure and the brake released. There was quite a bit of pressure. The rotor was very hot of course. I headed back home and by the time I got home it was locking again. I did the same bleed to release the pressure. I used my infrared temp gun and the rotor was well over 240 degrees. the left front brake isn't having a problem (it is working as I jacked up front wheel and checked that it is working) and not getting hot.

I took the line off the master cylinder and ran a small wire (bread tie) in the return hole. It appeared clean and clear. I noticed my rear pads were somewhat thin so I changed them and put it all back together and bled rear, front left and the tree location. I actually bled the tree location after the rear at first. When I opened that bleeder nothing came out so I took bleeder completely out and brake pedal was hard so I pushed hard and something white finally blew out and then fluid came out. Then I closed it up and bled rear again, then left front and tree.  Pedal felt good. I took it for a ride and in about 8 miles it started getting hot and rear locking up again.

I am at a loss for ideas since caliper will release when line or bleeder is opened.

[djh3]

Yup saw this several times in automotive world. More frequent for whatever reason on front brakes. So what happens over time is the rubber flex hose deteriorates inside. It can act as a one way valve so to speak. It will allow flow (pressure) to caliper, and then because pieces of the inside are blocking and there is not the pressure of your piston pushing the fluid it cant return on the very low pressure of the static return. So my somewhat educated guess (50+ years automotive) is the hose is kaput. You already did the troubleshooting. It had pressure, you released at caliper and it rolled free. Then it did the same action again. Shouldn't be to expensive to repair.

[Marcarl]

Two things can cause this to happen. One is that the rear reservoir is too full and when it heats up there won't be enough space the brake fluid to go, so the pads don't release completely and cause more heat. This can usually be fixed opening the rear bleeder screw.

Second, there is a weeeee little return hole in the MC and if it gets plugged then the same thing will happen, more than likely your issue by what you said about the white stuff. The ix would be to clean and flush the whole rear system, a lot of work but I think you may have had a puddle of water residing in the system. Do this sooner than later.

[saddlebum]

Also if you still have the linked braking system or delinked them yet left the proportioning valve in place on your bike,  remove and check the proportioning valve. it too gets loaded up with the white crud. Regardless which is the cause of you problem if you have not changed the fluid in a very long time, it would be worth your time to remove inspect and clean all and replace the brake line. You can get  brake lines from @skydoc_17

[skydoc_17]

Hey Ben,

Thank you Sir, for the kind words about the De-Link Kit I offer for the First Gens. That was Very kind of you. Now, about this rear brake issue!

Hey John, Both Marcarl and Saddlebum have touched on the MOST important points of the issues with the First Gen. rear brakes. I will list all of the things that I have come across during the time I have owned First Gens. (In no particular order) Because of the number of miles I ride every year, I change out my Brake and Clutch Fluid EVERY spring. ( I live in Pennsylvania, so we do not ride all year round) I found that replacing the fluids is much cheaper than repairing the damage that results from water collecting in the Brake and Clutch Systems. As mentioned above by the other two Forum members,  the metal internals of the proportioning valve becomes contaminated by the collection of moisture at that location. Another issue is the fact that if you look closely at the outside of the rear Master Cylinder fluid reservoir, you will see that casted right into the reservoir is a place for a sight glass, which was never finished. (ie, NO sight glass!) Because this Master Cylinder is located right next to the right rear exhaust header, it is exposed to a tremendous amount of radiated heat. More so than any other Master Cylinder. When filling this Master Cylinder, I fill it until when I stick my baby finger in the fill port, the brake fluid just barely touches the end of my baby finger. (In case you have stubby fat fingers, (NO insult intended!) the level should be about a good one inch below the fill port) This gives the brake fluid some room to expand due to the extreme heat it is exposed to. Another issue I have come across is the use of "High Friction" performance "HH" style brake pads on the rear caliper. The extra heat developed by these aggressive pads will also overheat the Brake Fluid, and if the Master Cylinder is overfilled, will cause a "Lock-Up" condition like you have described. Another issue is the fact that your brake and clutch lines are roughly 34 years old, the interior of these lines have started to decompose, as well as starting to balloon out during the braking process. This debris in the brake lines clogs up the  the proportioning valve, causing it to NOT allow the Brake Fluid to return to the reservoir, which locks up the rear brake caliper. Lastly, a warped Rear Brake Rotor will overheat the rear brake caliper, causing it to lock up. 

Well John, I know this looks like "The Long Way Around The Barn" so to speak, about this issue, but the point everyone is trying to make is that ALL of these issues can be addressed with some time and of course some MONEY! I try to justify the time and money by telling myself, "The Brake/Clutch System has functioned well for 34 years, if I spend the time and money to correct these issues, I should be good to go for another 30 plus years"! 

Because I do all of my own work, and have access to discounted parts from Yamaha due to my shop here in Pennsylvania, when I purchase a "new to me" First Gen. I usually replace ALL of the Master Cylinders as well as the Clutch Slave Cylinder right off the bat instead of replacing one part at a time until the Brake or Clutch System finally starts to function properly. I fully realize that not everyone has the mechanical ability and/or the finances to drop that kind of money/time on a 30 plus year old motorcycle!

Both the Braking System and the Clutch System of these motorcycles can be upgraded into the 21st century by the "Investment" in some new OEM parts as well as the addition of some "Performance" parts. (the De-Link Kit I offer is one of the Performance parts I am talking about) 

It has been my experience that this usually goes one of two ways. Option 1- you bite the bullet and spend the time and money to rebuild the Brake and Clutch Systems. Option 2- the braking system issues are NOT addressed, or piece mealed one part at a time until the bike is unrideable and it is sold for a very low amount of money or even worse, the bike is parted out! BOTH of the First Gens. that I currently own, (an 87'VR and an 89'VR) were both these kinds of bikes. I purchased them for a small amount of money, replaced ALL of the perishable brake and clutch parts right off the bat, upgraded the Line Set and switched to R1 Front Calipers and have been enjoying them ever since. 

So at this point John, you need to ask yourself, "Is this motorcycle worth the time and money to get it to brake properly"? If the answer is YES, then feel free to PM me and let's get some new parts on this bike before the summer ends! OR if the answer is NO, then there is a place on this forum where you can list your bike for sale or sell parts off of it. I personally hope the answer is going to be YES! I would hate to see another First Gen. end up being scrapped because of the time/money it would take to "Make it Great Again" LOL!

Thanks again Marcarl and Saddlebum for addressing this issue that plagues most of the First Gens. on the road today. I commend you John, for having the courage to ask for help on this Forum! Either way you decide to go here John, I hope it works out for you.

Earl.

[jdross440]

Thank you Skydoc_17. Where is the proportioning valve located?  I would like to spend some time looking thru the system to see what started this lockup and then replace they system. Like you said the original system is old. I do change the fluid about every 2 years. The brakes were working very good until it sat about 2 months then this happened. This bike only has 76K miles. I bought it in 2005 with 13K miles. Being in Arkansas, Summer heat slows riding down a lot.

[Marcarl]

Seeing as it's been sitting for quite some time, I think you'll find that the rear wheel cylinder might be hanging up.

[jdross440]

Only setting 2 months. It has set longer than this many times. When I relieve the pressure (either at banjo bolt or bleeder) it releases until I use the brake several times. Each time I use the brake I notice the pedal doesn't depress as far until it doesn't move. The left front isn't locking up.

[saddlebum]

It is not always about how long it sits. The age of the brake fluid is also a big factor as brake fluid will absorb moisture. I do not even save opened containers of brake fluid for more than a year and that is only for topping up purposes. I get a fresh container anytime I do a complete fluid change or brake job.

[BMW]

The brake pedal has a return spring on it, be sure that it is returning to its normal position when you release it.

[luvmy40]

Based on the OP's description of the repeated symptoms, I'd say it's debris/gunk in the proportioning valve, and/or the brake hose to the rear slave is delaminated and blocking return flow.

 

Definitely time for a flush and new hoses.

 

I have never been very good about maintaining brakes properly. I tend to ignore them until they fail in some manor. Stupid, I know, but it still a fact. I am going to make a concerted effort and set up a schedule to flush the brakes periodically and be more proactive.

I thought the brakes on my '83(all original parts) were good until I rebuilt the MCs and installed new hoses, Earl's delink kit. There was a night and day difference in the feel and performance.

[Christopher lee]

2 hours ago, luvmy40 said:

Based on the OP's description of the repeated symptoms, I'd say it's debris/gunk in the proportioning valve, and/or the brake hose to the rear slave is delaminated and blocking return flow.

 

Definitely time for a flush and new hoses.

 

I have never been very good about maintaining brakes properly. I tend to ignore them until they fail in some manor. Stupid, I know, but it still a fact. I am going to make a concerted effort and set up a schedule to flush the brakes periodically and be more proactive.

I thought the brakes on my '83(all original parts) were good until I rebuilt the MCs and installed new hoses, Earl's delink kit. There was a night and day difference in the feel and performance.

Sounds like definitely time change all your fluids do it yourself or taking somewhere to get a complete fluid change

[skydoc_17]

Hey John,

After hearing more details about the issue, I am going to agree with Marcarl on this one! At the very least, I believe the rear caliper is no longer functioning properly. (the caliper pistons are compressing, but NOT retracting) Which leads me to believe that the right front caliper is no longer functioning properly as well. This is the point I was trying to make earlier. Chasing the lack of function of one component at a time is frustrating and it compounds the labor to effect a total repair of the system. (either brake or clutch) This is what I meant by "Biting the bullet" and just rebuilding/upgrading the entire system ONE TIME, and getting on with the Riding part of this journey. Frankly, as long as the right front caliper wasn't locking up, how would you know if it was working at all?!?! Unlike the right front caliper, which is dedicated to the right front M/C, the left front and rear calipers are "Linked" together. There isn't really a good way to isolate either the right front or rear caliper to test them. At my shop, I have a "Test Fixture" where I can connect a single caliper to see if it is functioning properly. This is why I suggested rebuilding BOTH M/C's as well as ALL of the calipers right off the bat. One Job, One Time! 

The next few things I am going to speak about may seem a bit "Brutal", and I apologize in advance for the following comments! To rebuild the rear M/C and lets say the rear caliper but leave the right front caliper Un-rebuilt and expecting the 30 plus year old seals of the right front caliper as well as the old rubber brake lines to handle the increased fluid pressure of all of the other new parts you installed is extremely "Optimistic" in my opinion! Secondly, as scary as a rear caliper Lock Up is, a lock up of the left front caliper at almost ANY speed, (OR right front for that matter) puts you at a VERY HIGH RISK of an 800 pound motorcycle slapping you on the back of your helmet, as well as a "Date" with the pavement!!! What's you LIFE worth, John! Bragging about Road Rash at the age of 20 is "COOL"! Being subjected to Road Rash at 45-65 years old,  (or older, in my case) could be the end of my riding career. (Last brutal comment) You couldn't BUY the ash tray of a late model Gold Wing for what you have paid for your Venture. Personally, ANY bike I own NEEDS to GO properly, and STOP properly, that's a minimum requirement for me. Because of the way I ride, the three things I NEVER skimp on are Brakes, Tires, and a working Clutch System. Period! As my wife would say. "I'm Worth It"! Rant over. To find the proportioning valve, follow the rear brake line from the rear caliper to the valve.

Earl.