TomH Posted July 17 Share Posted July 17 Greetings again. My 2000 v11 surprised me a couple days ago with a rear brake… “miss” followed a few minutes later by a functional braking. How? Stepped down on the lever as per usual, lever gave no resistance, bike didn’t slow. No rear brakes. Later on, it worked. i know I have some learning to do, and could be doing something wrong, but this one I sat with when it went bad. I pulled into a gas station, got off and pushed the lever by hand. Nothing at all, I rolled the bike with the pedal on. I started home carefully and after a couple stoplights it worked again. can anyone explain this? Link to comment Share on other sites More sharing options...
docc Posted July 17 Share Posted July 17 Time to service/ lube the lever pivot and bleed the hydraulics. The caliper has to be removed and rotated to position the bleeder upward and above the master cylinder. Take time to clean the pistons, rotate them with a piston tool, and press them back into the seals. Polish and lube (silicone grease only!) the pad pin and spring. 3 Link to comment Share on other sites More sharing options...
PhillipLarsen Posted July 17 Share Posted July 17 You might also want to check that the master cylinder is working correctly and does not have any small pieces of debris contaminating the very small holes. One time my 04 V11 had a case where it started with no brake one time, like you mention and within a couple miles and uses of the rear brake had the brake on slightly all the time, overheating the pads and disc. If I had not noticed I think the disc would have turned red. The pads had started to break down from heat. The issue was a piece of debris in the small orfice where the 90 degree fitting comes out of the master cylinder. Looked like a tiny piece of black seal material. The brake had worked perfectly since new up to that time. I rebuilt the master cylinder, caliper and new pads and worked like new since. 2 Link to comment Share on other sites More sharing options...
Lucky Phil Posted July 17 Share Posted July 17 2 hours ago, TomH said: Greetings again. My 2000 v11 surprised me a couple days ago with a rear brake… “miss” followed a few minutes later by a functional braking. How? Stepped down on the lever as per usual, lever gave no resistance, bike didn’t slow. No rear brakes. Later on, it worked. i know I have some learning to do, and could be doing something wrong, but this one I sat with when it went bad. I pulled into a gas station, got off and pushed the lever by hand. Nothing at all, I rolled the bike with the pedal on. I started home carefully and after a couple stoplights it worked again. can anyone explain this? I'd be looking at your rear wheel bearings first thing just to be safe. Don't bother with squatting down and trying to twist it, grab a 3 foot length of timber and put some tape on it to protect the paint and stick it between the swingarm and tyre sidewall and lever the wheel and see if it moves. The situation is when the bearings are shot badly enough cornering forces mean the wheel twists a little which pushes the brake pads back into the calliper enough to lose the brake. Then some straight riding and a few pumps on the pedal brings them back onto the disk. If you've picked up some rattly vibes in the footpegs lately thats also a good sign of bad rear wheel bearings. Phil 1 1 Link to comment Share on other sites More sharing options...
gstallons Posted July 17 Share Posted July 17 You want brakes not 99.9999% of the time , you want brakes 100% of the time . Use DOT 4 fluid straight from a new bottle . How many pumps did it take to get a good pedal ? I know counting is the last thing on your mind . Just wondering. Have you ever flushed / bled the rear brake system ? Link to comment Share on other sites More sharing options...
GuzziMoto Posted July 17 Share Posted July 17 If you hit the rear brake and there is no brakes there, the first thing I would do right then and there is pump the brake pedal to see if the brakes come back. Having to pump the brakes can happen because the brake pads get pushed away from the disk. That can happen for a few reasons, including what Phil mentioned of having issues with the wheel bearings. If the wheel has enough wobble in it from loose bearings the disk can push the pads away from it when it wobbles. It does not take a massive amount of wobble to do that. It only has to push the pads a tiny amount away from the disk. Anything that causes the pads to be pushed away from the disk will cause the brakes to not be there when you next push on the brake pedal. But if that is the issue successive pumping of the brake pedal will normally restore brake function. Other things can also cause brake issues, like the hole between the master cylinder (the part pushing the brake pedal acts on) and the reservoir. That hole must be open when the brake pedal is in its normal position. Improperly adjusting the brake pedal can cause that hole to not be open when the brake pedal is not being pushed. Or you could have a small piece of debris clogging that hole, as mentioned. You could also have issues inside the master cylinder. There is a small spring inside it that pushes the piston back when you release the brake. If that spring can't or won't push the piston back when you release the brakes you will experience brake issues. 1 Link to comment Share on other sites More sharing options...
docc Posted July 17 Share Posted July 17 10 hours ago, Lucky Phil said: I'd be looking at your rear wheel bearings first thing just to be safe. Don't bother with squatting down and trying to twist it, grab a 3 foot length of timber and put some tape on it to protect the paint and stick it between the swingarm and tyre sidewall and lever the wheel and see if it moves. The situation is when the bearings are shot badly enough cornering forces mean the wheel twists a little which pushes the brake pads back into the calliper enough to lose the brake. Then some straight riding and a few pumps on the pedal brings them back onto the disk. If you've picked up some rattly vibes in the footpegs lately thats also a good sign of bad rear wheel bearings. Phil I completely forgot this happened to mySport five years ago! In that case, @TomH, be certain your inner rear wheel spacer measures correctly and use high quality bearings (I settled on KOYO) . . . 1 1 Link to comment Share on other sites More sharing options...
TomH Posted July 19 Author Share Posted July 19 On 7/16/2024 at 9:45 PM, gstallons said: You want brakes not 99.9999% of the time , you want brakes 100% of the time . Use DOT 4 fluid straight from a new bottle . How many pumps did it take to get a good pedal ? I know counting is the last thing on your mind . Just wondering. Have you ever flushed / bled the rear brake system ? Not yet, will be soon! 1 Link to comment Share on other sites More sharing options...
pete roper Posted July 19 Share Posted July 19 If the brakes haven’t been bled for an age the main piston seal in the master cylinder may be collapsed and not sealing properly. 2 Link to comment Share on other sites More sharing options...
gstallons Posted July 19 Share Posted July 19 IF the problem were involving air gap (clearance) at the brake pad/rotor , the problem would exist all the time . The problem would have to be at the master cylinder. Bleed the brakes if you feel capable . Remember you will have to remove and turn the caliper u/s down to bleed properly . Use DOT 4 fluid only and this is a two man operation. Link to comment Share on other sites More sharing options...
Lucky Phil Posted July 19 Share Posted July 19 53 minutes ago, gstallons said: IF the problem were involving air gap (clearance) at the brake pad/rotor , the problem would exist all the time . The problem would have to be at the master cylinder. Bleed the brakes if you feel capable . Remember you will have to remove and turn the caliper u/s down to bleed properly . Use DOT 4 fluid only and this is a two man operation. Not really. Re read my scenario and you might understand the scenario better. I've had this issue on a Ducati ST2 front brakes with a badly worn wheel bearing. Not saying it's the issue for the OP but it's worth spending 5 min to check the wheel bearings. Brake pads only clear the disk by maybe .005" thousands of an inch in normal operation when the brakes are released so it only requires the pads being pushed back 1/2 mm total to lose the brakes entirely. In the case of the Ducati front brakes you got good lever after riding in a straight section of road and coming to a stop. Full lever and normal travel. Take off and ride it around a corner and the next stop the lever's coming back to the bar. Give the lever a second pump and they're back to normal as is the next stop if you rode in a straight piece of road. Throw in a corner and you lost the lever again. Lateral wheel movement during cornering pushing the pads back but not in straight line riding. Phil 1 Link to comment Share on other sites More sharing options...
LaGrasta Posted July 19 Share Posted July 19 Buy one of these before you start. https://www.motionpro.com/product/08-0143 1 Link to comment Share on other sites More sharing options...
activpop Posted July 19 Share Posted July 19 37 minutes ago, LaGrasta said: Buy one of these before you start. https://www.motionpro.com/product/08-0143 I would be leary of the check valve not being up to snuff or as instantaneous as it needs to be. I never had a problem bleeding brakes by myself. Link to comment Share on other sites More sharing options...
gstallons Posted July 19 Share Posted July 19 3 hours ago, LaGrasta said: Buy one of these before you start. https://www.motionpro.com/product/08-0143 All MotionPro stuff is similar to SnapOn : expensive= yes / most righteous=YES 1 1 Link to comment Share on other sites More sharing options...
LaGrasta Posted July 20 Share Posted July 20 (edited) I actually bought a generic version of this tool over 20 years ago and absolutely love it, and rely on it. I use for both, cars and motos. Edited July 20 by LaGrasta Link to comment Share on other sites More sharing options...
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