5th Gen front brake lever "sag"

I have been unable to come up with a solution for this problem I'm having... Here's what happens, starting somewhere in the middle of the scenario:

• After a few weeks (or days, depending on how much riding), the front brake lever becomes soft, spongy like there is air in the line(s).
  
• I pump the front lever a few times quite hard.
  
• Lever recovers to "high and tight" (or as little travel and most feel you can get with factory brakes/lines).
  
• Feels great for a while, I forget about the problem.
  
• GoTo (1)

The other problem is the same happens with the rear...

Bike has 50k miles. Master cylinder "rebuilt" (piston removed, seals replaced, dust cover replaced) about 10k ago; rear has not been touched based on the condition of the front. All pads have less than 5k miles, bike is ridden fairly gently and when not spongy, the brakes perform flawlessly. Caliper piston seals were replaced about 15k ago because the fronts were dragging too much (turned out to be a worn/warped rotor...)

I have bled the brakes using the factory prescribed method using both a vac pump and then re-doing with the crack-the-bleeder-and-squeeze-then-tighten-bleeder-then-release-lever method as well.

It may be that I just need to re-bleed, but I wanted to post because I can understand (and have felt) when there is just air in the lines, levers are spongy; crack the bleeders, air goes out, problem solved. This deal about being able to "pump them up", though, has been annoying to say the least. However, as above, I did have to drain the whole system for the caliper seal replacement. After that was completed and bled, there were no problems for a few thousand miles.

Thoughts?

Thanks :)
Alex

I am sure that someone will quickly point out that the front and rear systems are tied together, one does not work without applying the other at the same time. A low-tech ABS sort of, if you will.

[image: View Post]flavadave98VFR800FI, on 20 October 2010 - 12:52 PM, said:

I am sure that someone will quickly point out that the front and rear systems are tied together, one does not work without applying the other at the same time. A low-tech ABS sort of, if you will.



This depends on the model he owns.....

Current VFR's may have linked brakes, prior gens have not.....

I have bled the brakes using the factory prescribed method using both a vac pump and then re-doing with the crack-the-bleeder-and-squeeze-then-tighten-bleeder-then-release-lever method as well.

At 50K the first question in my mind is are the hoses OE? The fact that it happens front and rear makes me think "air". Your described manual bleed sequence is out of order if this is the way you intended to write it. Try this order:
1. Pump up with lever
2. Crack bleeder while holding lever solidly.
3. When all pressure at the lever is gone, tighten the bleeder THEN release the lever.
4. Repeat a few times as necessary.
Good luck to you.

[image: View Post]Ottoman, on 20 October 2010 - 04:30 PM, said:

I have bled the brakes using the factory prescribed method using both a vac pump and then re-doing with the crack-the-bleeder-and-squeeze-then-tighten-bleeder-then-release-lever method as well.

At 50K the first question in my mind is are the hoses OE? The fact that it happens front and rear makes me think "air". Your described manual bleed sequence is out of order if this is the way you intended to write it. Try this order:
1. Pump up with lever
2. Crack bleeder while holding lever solidly.
3. When all pressure at the lever is gone, tighten the bleeder THEN release the lever.
4. Repeat a few times as necessary.
Good luck to you.


The steps you state are what I tried to has said...

I know the problem isn't some sort of bad pixie dust, so I'm going to go through the bleeding process again. I think the problem likely started with having to drain the system to replace the piston seals... I got the system refilled, but I can't get past the thought that there must be air in there somehow. Also, the master is about 3/4 full, so not overfilled nor sucking air. I just don't know how/why it changes over time.

[image: View Post]Dutchy, on 20 October 2010 - 02:46 PM, said:

[image: View Post]flavadave98VFR800FI, on 20 October 2010 - 12:52 PM, said:

I am sure that someone will quickly point out that the front and rear systems are tied together, one does not work without applying the other at the same time. A low-tech ABS sort of, if you will.



This depends on the model he owns.....

Current VFR's may have linked brakes, prior gens have not.....


Well, profile says a yellow VFR, so I'll assume it's a 5th gen. Also, linked braking system /= low tech ABS. It means that applying the front brake also sends some braking to the rear, and vise versa.

There are a couple of good write-ups on the order of bleeding brakes on here. Make sure you do it in the right order.

The brakes are going to build up pressure the more times you squeeze it, then it will get a bit softer if you don't use it for a while. Shouldn't be spongy though. Have you tried tapping the lines to see if any air bubbles come out?

Try this;
Get a zip-tie, apply the front brake, and tie the lever back onto the bar, leave over night, but as long as possible. The theory is the air bubbles will rise to the top and escape through the res if you give them the chance.

I am not sure the exact science, but it worked for me when I had the same problem. I bleed, and bleed, still couldn't get them right until I did this and after 48hrs they were great.

[image: View Post]Stealth, on 20 October 2010 - 08:56 PM, said:

Try this;
Get a zip-tie, apply the front brake, and tie the lever back onto the bar, leave over night, but as long as possible. The theory is the air bubbles will rise to the top and escape through the res if you give them the chance.

I am not sure the exact science, but it worked for me when I had the same problem. I bleed, and bleed, still couldn't get them right until I did this and after 48hrs they were great.


+1. Let it sit for a while, tap gently on the lines to help unstick any airbubbles, and repeat a few times. Then let it sit. You've already tried the full flush, so this can't hurt.

[image: View Post]Stealth, on 20 October 2010 - 08:56 PM, said:

Try this;
Get a zip-tie, apply the front brake, and tie the lever back onto the bar, leave over night, but as long as possible. The theory is the air bubbles will rise to the top and escape through the res if you give them the chance.

I am not sure the exact science, but it worked for me when I had the same problem. I bleed, and bleed, still couldn't get them right until I did this and after 48hrs they were great.



I had a similar problem with one of my bikes and tried the same thing..... it didn't work. In fact, I tried a couple of times with the same result. What it nets is the same as bleeding the brakes: a nice firm lever for the first ride. After a day or so of sitting it goes right back to squishy again.

I wish that I could help, but I never did find a solution on that bike.

Would anyone else agree that if it still has to be pumped up to gain pressure and you feel that the bleed itself is not the issue, then you need to return to where you started? The master could be the issue if the bleeding is not solving the problem?

Have your buddy take all the same steps in the bleeding process. Sometimes your just to close to the issue to see what you have missed.

I don't have any issues like yours, I just dislike the linked system on general principle! :beatdeadhorse:
In any case, try bleeding from the master banjo bolt. Most new masters now come with bleeder screws because this is the highest part of the system, so it should be bled from there. Same idea as the bleeder screws, just messier. Squeeze, crack the banjo slightly until fluid starts to come out, and tighten as the lever hits the bar. Repeat a couple times, just for fun! Get some towels or shop rags to catch the fluid.

[image: View Post]KPerham, on 21 October 2010 - 12:26 PM, said:

I don't have any issues like yours, I just dislike the linked system on general principle! :beatdeadhorse:
In any case, try bleeding from the master banjo bolt. Most new masters now come with bleeder screws because this is the highest part of the system, so it should be bled from there. Same idea as the bleeder screws, just messier. Squeeze, crack the banjo slightly until fluid starts to come out, and tighten as the lever hits the bar. Repeat a couple times, just for fun! Get some towels or shop rags to catch the fluid.


The simpler & less messy way to accomplish this is to burp the master - take off the cap, plastic breather plate, and rubber diaphragm. Remove the master from the bar, hold it in your hand & tip it s othe fluid orifice in the bottom is now the highest point in the system. Tap the banjo with the plastic end of a screwdriver 2-3 times. Now pull the lever just slightly. You will see bubbles come out of the fluid orifice.