Front brake inconsistent resistance

[ChiefJP_imp]

All,

DLX w 8.6k miles. Was backing out down a driveway with a slight incline and went to use the front brake to slow it a bit. To my surprise, there was barely any resistance to the brake lever. The lever almost went to the bar. I did get some stopping power out of it so that was good but it was a bit of a shock. First time that has ever happened.

So then I made an appt with my local Honda dealer to flush and replace all the fluids (brake, clutch) because I bought the bike used and wasn't exactly sure of the complete maintenance history.

Anyway, long story short-ish, I got the bike back and I'm still noticing wild swings in brake lever resistance even with new fluid. I can always get pressure back up with a few pumps but it starts to fade with maybe 10 minutes or so of riding.

Any thoughts from the group?

My guess is most will say there is air in the line but I find it a bit odd that air would be in the line both before and after the service. Maybe though?

Thanks for any feedback. Calling the dealer tomorrow to see what they think.

 

[Cormanus]

Chief, years ago I had a car that did that. The problem was in the slave cylinder.

 

[ChiefJP_imp]

Chief, years ago I had a car that did that. The problem was in the slave cylinder.

Thanks Cormanus!

 

[peterbaron]

You probably meant the brake master cylinder, not slave.
:beerchug:

 

[Cormanus]

No. I didn’t PB. At the time I was told it was the slave cylinder. But it’s 50 years ago so I don’t remember the details.

 

[peterbaron]

Hmm, that's strange, as I never heard about cars having brake slave cylinder but brake wheel cylinder for drums or calipers for disc.
But we both might be correct as some parts are named differently in different word's region.
As to hydraulic operated clutch, yes, it has a slave cylinder.
Anyhow :beerchug:

 

[Cormanus]

Ah, yes, now you mention it, it was the clutch, Peter.

Apologies, Chief. That was no help at all.

 

[peterbaron]

Well, it still could be as the hydraulic circuit malfunction.

 

[Lord Popgun]

Sounds like a problem in the (front) master cylinder to me

 

[max]

( can't help myself ) If there is loss of fluid ( the reservoir level is dropping ) it's anything but the master cylinder ( at the handle bars ).
And if there are no leaks it IS the master which is letting fluid getting past the first sealing rubber cup ( there are two, one for pressure and the second one which you can see in the reservoir opening to stop fluid leaking out of the cylinder ).
The fact that it restores itself with a few pumps suggests to me that it does point to the master once it resets itself.

Could be the brake is not used frequently or a myriad of other causes, one of which is corrosion in the cylinder,worth a look, easy to replace the parts on the handlebars and should quickly prove the point, not a usually mentioned fault if i recall correctly.
Here's how it works;



All the best with the bike Chief.

 

[mvk24_imp]

2 things I can think of.

1. Outright issue at the front master cylinder as mentioned above. (If not seeing any leaks at either front calipers or lines.

OR

2. You had air in the lines and also happened to have a new tech/apprentice at the shop that didn't bleed your brakes properly and you still have air or the addition of air in the system.

I would absolutely start with flushing your brakes yourself to purge any air and know for sure that it is done and done properly. You can even get a vacuum hand pump from harbor freight for a few dollars that makes it an already easier and faster process. You'll be done in about 5 minutes.

https://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-63391.html

There are other pumps on amazon also for $20 or less. You also don't need a pump you can just do it the old school way by building pressure with the lever, holding the lever, and opening then closing the bleeder, then releasing the lever and repeating. Just make sure you keep the master cylinder topped off.

After you flush the system to make sure for certain there is no air in the system AND that you actually have new brake fluid. If the problem still persists than you can go deeper into rebuilding the calipers or master cylinder after further investigation.



2014 CB1100, 1981 KZ440 LTD, 1993 Yamaha XJ600 Seca, 1994 Yamaha XJ600 Seca

 

[ChiefJP_imp]

( can't help myself ) If there is loss of fluid ( the reservoir level is dropping ) it's anything but the master cylinder ( at the handle bars ).
And if there are no leaks it IS the master which is letting fluid getting past the first sealing rubber cup ( there are two, one for pressure and the second one which you can see in the reservoir opening to stop fluid leaking out of the cylinder ).
The fact that it restores itself with a few pumps suggests to me that it does point to the master once it resets itself.

Could be the brake is not used frequently or a myriad of other causes, one of which is corrosion in the cylinder,worth a look, easy to replace the parts on the handlebars and should quickly prove the point, not a usually mentioned fault if i recall correctly.
Here's how it works;



All the best with the bike Chief.

Whoa! These diagrams are awesome. Thank you!. Also, just gunna throw out that there doesn't seem to be fluid leaking from anywhere. No fluid drop in the reservoir that I can see.

Thanks again all.

 

[GoldOxide_imp]

You probably meant the brake master cylinder, not slave.
:beerchug:

Aren't "master" and "slave" words politically incorrect and deprecated?

If so, it will be interesting what the industry replacement words will be.



(Got this idea when speaking about a home's master bedroom. Responses were disapproving.)

 

[1973cb750]

didnt read the whole thread but greasing the pivot point and where it contacts the piston helps big time on clutch and brake i do it twice a year

 

[Rocky_imp]

( can't help myself ) If there is loss of fluid ( the reservoir level is dropping ) it's anything but the master cylinder ( at the handle bars ).
And if there are no leaks it IS the master which is letting fluid getting past the first sealing rubber cup ( there are two, one for pressure and the second one which you can see in the reservoir opening to stop fluid leaking out of the cylinder ).
The fact that it restores itself with a few pumps suggests to me that it does point to the master once it resets itself.

Could be the brake is not used frequently or a myriad of other causes, one of which is corrosion in the cylinder,worth a look, easy to replace the parts on the handlebars and should quickly prove the point, not a usually mentioned fault if i recall correctly.
Here's how it works;



All the best with the bike Chief.

Excellent illustration

 

[max]

( can't help myself ) If there is loss of fluid ( the reservoir level is dropping ) it's anything but the master cylinder ( at the handle bars ).
And if there are no leaks it IS the master which is letting fluid getting past the first sealing rubber cup ( there are two, one for pressure and the second one which you can see in the reservoir opening to stop fluid leaking out of the cylinder ).
The fact that it restores itself with a few pumps suggests to me that it does point to the master once it resets itself.

Could be the brake is not used frequently or a myriad of other causes, one of which is corrosion in the cylinder,worth a look, easy to replace the parts on the handlebars and should quickly prove the point, not a usually mentioned fault if i recall correctly.
Here's how it works;



All the best with the bike Chief.

Excellent illustration

Excellent illustration
Hi Rocky, good to see you

 

[bvictory_imp]

Considering that the front brakes are probably the most important safety system on your bike, I would get that addressed asap. There might be residual air in the line. Even with a brake bleed, I once had air in my rear brake line. I bungee corded the foot lever as far as it would go and left it overnight. Then I came out in the morning and bled it again. That fixed it. Try the same process with your front brake lever. Make sure you attach a hose to the nipple on the caliper and slowly open it. Let it bleed slowly and watch the brake fluid level and make sure it stays filled so more air doesn’t get in there. If that doesn’t work, I think you need to have your master cylinder rebuilt.