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?


Sent from my iPhone using Tapatalk

 

[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]

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]

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]

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.

 

[MNKeith]

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.

Interesting. I'm not doubting you but I'm confused why that would cause an issue? Mine looks to be in good shape but it's an easy swap if I still have issues in the next few weeks.

Edit. Just saw his post. I think his was more of a spongy feel problem but nevertheless, good to know.

 

[(F5)]

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

This one.

Also check the free play of the lever. It is well conceivable that the beedhole is obscured by lever adjustment. Almost. When it gets hot it does obscure.

 

[hadfield4wd]

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

I had this problem with a RM125 I had. But the brakes locked up. The bleed hole blockage will not allow the piston to "return".

 

[MNKeith]

Much delayed follow up... Did some poking and cleaning of the master cylinder, several rides since and I seem to have improved feel on the lever now. It doesn't get hard like it did before (that's what she said.)

 

[(F5)]

Cool, yeah the getting harder was a dead giveaway that the return wasn't occurring properly.

As an aside, I've just been through my both calliper slide bolts and replaced them on my 07. Didn't cost much the sliding one was corroded and mid shapen and the pad one was grooved on both. Pads can hang up and pivot there.

 

[MNKeith]

A year and a half later and I was at the same point.

Brake always worked, just lacked feel and I'm not a AA rider so priority level lost out to drinks on the patio most of the time.

I bled different ways. I replaced lines. I rebuilt the MC. I cleaned the MC. I swapped the MC.

Sometimes I'd get slight improvement, but then back to rock hard.

Never had irregular wear on the pads and didn't see how the caliper could cause this.

Welp. Swapped calipers yesterday. BIG difference. Normal lever travel and progressive front braking. I have yet to get in to the old caliper and see if the seals or pistons are wonky, but whatever is going on, that was the culprit.