Crazy Brakes

[sAsLEX]

As those of you on the Coro loop with me a while back would remember , about 5k short of Tairua my brakes went from there normal a little pull back and then nice and progressive, to only requiring the slightist touch on what would be described as a very hard lever.

Now the road side diagnosis was an over full resivour, so fixed that in a jiffy, and the brakes kinda went back to normal, cept for the huge fade they suffered down the west coast of the loop.

Now I have noticed over the past couple of weeks that whenever I saddle up after the bike has been sitting in the sun/heat for a while the brakes are again very "hard" with bugger all pull required.

This happened again yesterday and for some reason I gave the brake lever a push with the back of my fingers forward, and the brakes went back to normal.

Would/could this be a problem with the master cylinder, was thinking that maybe the lever is not going back out far enough and uncovering the little hole that lets the fluid back in to the resivour, or that this little hole is blocked?

Any other ideas?

[sAsLEX]

The callipers were overhauled a year ago, so dont think they would be the problem.

[bugjuice]

try a straight up fluid change. Dump all of the old stuff and go get some clean new stuff. The master cylinder bit could be getting old too.. those are about 30 bucks from memory, and isn't hard to do them yourself

[sAsLEX]

try a straight up fluid change. Dump all of the old stuff and go get some clean new stuff. The master cylinder bit could be getting old too.. those are about 30 bucks from memory, and isn't hard to do them yourself

fluid is only a week or two old , problem was happening before ad after, hmmm might find out about these master cylinder things

[bugjuice]

k, well that rules that out.

your brakes only consist of a few things, so it can't be hard to source the problem. Go order a master cylinder kit, and it's a doodle to replace. you'll be pissed cos you just spent about 30 bucks on a spring, a rubber boot and a few rubber washers, but it could make a lot of difference..

next would be the lines. Then after that, you're shit out of options.. try checking under the seat..?? :spudwhat:

[Two Smoker]

Just do a full brake over haul... shouldnt cost too much... The thing that puzzles me is the lever getting hard part... A stuffed master cylinder seal usually results in the lever pulling back to the bar fully, but progressively...(you can generally feel the fluid bleeding through if you pull hard on the lever...)

[wendigo]

my moneys on the spring getting old & tired & not having enough strength to push the piston in the master cylinder back far enough to uncover the hole to the fluid resevoir.

Hence each time the brake system gets warm (like in the sun) the fluid in the lines expands, but has nowhere to go, hence the impression that the brakes are hardening up.

[imdying]

Sounds like you've over adjusted the free play screw in an effort to make the brakes 'feel' better.

[Motu]

Check your lever adjustment first,you need free play when the fluid is hot.Other wise the seals are swollen,and the rear seal is not opening the compensating port.

[HDTboy]

my moneys on the spring getting old & tired & not having enough strength to push the piston in the master cylinder back far enough to uncover the hole to the fluid resevoir.

Hence each time the brake system gets warm (like in the sun) the fluid in the lines expands, but has nowhere to go, hence the impression that the brakes are hardening up.

Wot he said

[imdying]

Be suprised if the spring had worn out, unless it's old and British that is a pretty unlikely scenario. I'm with Motu on the blocked compensating port though, perhaps you cleaned it with something that had traces of petroleum when you changed the fluid? Carb clean? CRC? or the like? Anything like that will make the seals swell... of course age and not changing the fluid can make them swell too. Try the simple things first though, have a look at the adjustment screw, it's a pretty common mistake to make.

[dhunt]

I had a similar problem when I welded a little blob onto the inside of the brake level so that I didn't have to pull the level in so far for it to start braking. This resulted in the brakes actually locking on solid after they warmed up a bit .

I think this could be similar to what you were experiencing as the brake fluid couldn't drain properly back into the master cyclinder after using the brakes.

Why this would be happening to you I'm not sure, possibly the return spring isn't as good as it should be any more???

[sAsLEX]

Just do a full brake over haul... shouldnt cost too much...

Costs heaps and takes ages for the parts to come from Japan, did one a year ago on the callipers with the Help of your esteemed mecahnic Milky

my moneys on the spring getting old & tired & not having enough strength to push the piston in the master cylinder back far enough to uncover the hole to the fluid resevoir.

Hence each time the brake system gets warm (like in the sun) the fluid in the lines expands, but has nowhere to go, hence the impression that the brakes are hardening up.

Thats sounds exactly like whats happenin, No haven't adjusted anything Motu since I had it but that could be the prob (especially since it fixed when I pushed it forward with me fingers. Definatly sounding like it is the hole being blocked, will have another look tonight

Be suprised if the spring had worn out, unless it's old and British that is a pretty unlikely scenario. I'm with Motu on the blocked compensating port though, perhaps you cleaned it with something that had traces of petroleum when you changed the fluid? Carb clean? CRC? or the like? Anything like that will make the seals swell... of course age and not changing the fluid can make them swell too. Try the simple things first though, have a look at the adjustment screw, it's a pretty common mistake to make.

Never clean with anything other than braklean made by crc, or fresh fluid. Have only flushed the old fluid out with new fluid for the past year. Will have a lookk at that adjustment screw though.

Cheers for your ideas everyone.
Oh and best place for these master cylinder kits? it is a Honda so Kerry at motohaus? or ........ cyclespot .....

[bugjuice]

if they're not in the country, then they'll all go thru the main distributor, and if it's cyclespot, then it'll end up going thru them whoever you go to..

[sAsLEX]

if they're not in the country, then they'll all go thru the main distributor, and if it's cyclespot, then it'll end up going thru them whoever you go to..

depends where I want some of my money to go as profit then, off to ring Kerry