Losing feel in front brake

[MNKeith]

Confused.

I have an '08 EC250 with a front brake that has a mind of it's own. When cold, I have normal lever feel. After a brief amount of riding, the lever travel shortens dramatically and is quite stiff. The front brake still operates but I lose leverage with the shortened pull and the feel just isn't very good. It doesn't seem to return to what I deem normal until the bike has been put away for the day.

This problem has been the same through:

Various brands and flushes of fluid.
Varying amounts of fluid in the master (from bottom of sight glass to top)
Multiple brake pads
And now on a brand new front brake line (replaced due to wear)

Now I'm on to either the caliper or the master? Or something I'm not thinking of. Any experience or thoughts on this?

[memphis2857]

Take the caliper apart and rebuild/clean it. It's probably all cruddy and when it gets hot the tolerances in moving parts gets tighter and it gets sticky.....maybe?


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[Rick]

Try putting a zip tie on the lever and throttle grip, pull it tight with a good amount of pressure. If there is a bubble it will work it's way back to the master cylinder... I'd try this first....could be an air issue.

[twowheels]

Originally Posted by Rick

Try putting a zip tie on the lever and throttle grip, pull it tight with a good amount of pressure. If there is a bubble it will work it's way back to the master cylinder... I'd try this first....could be an air issue.

I would have thought the same if it got spongy when riding, but not the other way around. Rebuilding the slave and master seem like good routes to follow.

[MNKeith]

I'm very confident it's not an air issue.

I'll dig into the caliper first and see what I find. Gotta take that off this week for some unrelated maintenance anyways.

[gasgasman]

Check the slide pins on the caliper. They may be binding when hot.

[MNKeith]

Well I diverted my night of working on the bathroom project to work on the bike a little instead. More fun.

Took the caliper apart. Gave the pistons a light sand and greased up the slide pins. No obvious issues anywhere. The lever does feel a little better now but that could also be some placebo going on.

Might leave it alone and see how it is when I ride it next week.

[RBrider]

Originally Posted by MNKeith

Well I diverted my night of working on the bathroom project to work on the bike a little instead. More fun.

Took the caliper apart. Gave the pistons a light sand and greased up the slide pins. No obvious issues anywhere. The lever does feel a little better now but that could also be some placebo going on.

Might leave it alone and see how it is when I ride it next week.

I had this same problem with my '01 200 with Nissin brakes.
Check the tiny bleed hole in the bottom of the master cyl reservoir. Run a tiny strand of copper wire thru it to make sure it is clean and 100% open.

RB

[MNKeith]

Originally Posted by RBrider

I had this same problem with my '01 200 with Nissin brakes.
Check the tiny bleed hole in the bottom of the master cyl reservoir. Run a tiny strand of copper wire thru it to make sure it is clean and 100% open.

RB

ooh. Will do, thanks!!

[Moto7man]

Check and replace the bleed nipple on the caliper, someone else had the same problem and the bleed nipple was deformed. He had the same inconsistent braking problem that you are having and it actually caused him to crash and get hurt. Then he traced the problem to the deformed nipple, he replaced it and braking problem solved.