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.

[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

[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.