Yet again I'm finding myself stumped by my not so humble k3. For the last 3 months or so my front brake has gotten more and more spongy. So finally after my bike got serviced I re built my font caliper and master cylinder. Only problem is nothing has changed. I'm at a total loss. From what I was able to measure everything was within spec. Any possible solutions?

Quote from: aussiegs on January 01, 2012, 04:32:49 AM
Yet again I'm finding myself stumped by my not so humble k3. For the last 3 months or so my front brake has gotten more and more spongy. So finally after my bike got serviced I re built my font caliper and master cylinder. Only problem is nothing has changed. I'm at a total loss. From what I was able to measure everything was within spec. Any possible solutions?

When you say "spongy" do you mean that when you squeeze the lever, if you don't squeeze it fast enough, you'll get all the way to the end of its travel with little/no braking?

One possible issue is water in your fluid. Does it seem like it gets better or worse after you've gone for a ride versus just letting it sit overnight?

Yeah the lever doesn't feel firm has little travel I'm not even game to take it out cause I know it won't pull me up. As for the diaphragm under the cap on the resiviour that could be it, it doesn't matter if it's on or off so maybe that.

But on second thought it should not matter because it's spongy either way. Just thought of that.

Quote from: aussiegs on January 01, 2012, 04:57:31 AM
Yeah the lever doesn't feel firm has little travel I'm not even game to take it out cause I know it won't pull me up. As for the diaphragm under the cap on the resiviour that could be it, it doesn't matter if it's on or off so maybe that.

But on second thought it should not matter because it's spongy either way. Just thought of that.

Well, if you haven't already, I would go ahead and flush the fluid and replace with new. That might fix your problem if it's old or has water in it.

Is the hose rubber or braided steel? If it's rubber, how old is it?

Most likely, just needs a good flush and new fluid like Kijona said.

Hose is rubber and original. From 03. And since I've only just re built the brakes of course the fluid has been replaced with fresh dot 4. And I've tapped on the fittings and caliper to make sure every drop of air is out. I've read the thread about hoses and this week I'm getting it replaced with a braided line but I'm doubtful it's gonna do much.

Quote from: aussiegs on January 01, 2012, 05:50:19 AM
Hose is rubber and original. From 03. And since I've only just re built the brakes of course the fluid has been replaced with fresh dot 4. And I've tapped on the fittings and caliper to make sure every drop of air is out. I've read the thread about hoses and this week I'm getting it replaced with a braided line but I'm doubtful it's gonna do much.

With such a simple device like hydraulic brakes...there isn't much that can be the source of the issue you are describing. What do you mean when you say "rebuilt" the master cylinder? It could be the little plunger that the brake lever pushes against...that's the only other thing I can think of.

So you've flushed and bled the brakes. That should rule out moisture and the fluid boiling.
Possible you still have air in the system. When bleeding I've found it necessary to give the brakes time to settle after bleeding and then re-bleed the next day to remove the last traces of air.

Although spongy, when you apply the brakes do they hold pressure? If they don't, then you have a leak. If they do, then something in the system has give to it. Either air in the system or the only other flexible component is the brake line, it's possible the brake line is ballooning or otherwise deteriorated. if it's an internal break down you may not see it. The Suzuki owners manual recommends the brake lines be replaced every 4 years.

When I re built it I put new seals on the plunger and measured it to make sure it was in spec. Inspected the bore to make sure it was ok (didn't have telescopic gauges to measure it ). And put new seals in the caliper and measured the pistons to make sure they were in spec (couldn't measure the bore cause no telescopic gauge due to the caliper setup). So the bores could be worn out I don't know. And yes bike has sat overnight and I've come back next day to have a crack at it and bled the line a little again but no bubbles. Something is not doing its job and there's not much to it I'm suspecting my bore of my master is gone because a month back when the sponginess was getting worse the break lever wasn't smooth it's was 'creaking' like seizing nearly I had to spray some inox on there to get it to smoothen up. But like I said the bore looked ok when I cleaned and inspected it but with no way to measure it yet I don't know.

Does the caliper slide freely on its pins?

Yep

A braided steel line will make a world of difference. Plus, brake lines are supposed to be replaced every 3 (or is it 5?) years. So if that's the original hose, you may have found the culprit.

When I bleed my brakes, I hang the master cylinder as high as possible with steel wire from the ceiling. That way it causes any air to naturally come up to the MC.

I find it weird that you need to replace your lines. In a car I've never had to replace them. But yes I can see your line of thinking.

Quote from: aussiegs on January 01, 2012, 06:47:32 PM
I find it weird that you need to replace your lines. In a car I've never had to replace them. But yes I can see your line of thinking.

Well, it all depends man, really. My 97 has original brake lines and the brakes are actually better than my 2007.

The steel lines will make braking much better, though I've found stock braking quite adequate for every day use. The reason is because the braided steel line will not "swell" under pressure like the rubber will. This translates into all of the "squeeze", or most of it anyway, being transferred to the brake calipers.

Good luck with it dude. You might need to replace a few parts but at least it's simple to fix.

Hey I totally get the reasoning behind braided lines, don't get me wrong but yeah looks like I'm up for component replacement here.

I think the problem is a lack of milk in the handlebars 

Michael

 

Quote from: mister on January 01, 2012, 11:01:27 PM
I think the problem is a lack of milk in the handlebars 

Michael

A lot of people never understand this theory. It's not just plain old 2% milk that is required, its evaporated milk. The dry white substance helps balance the handlebars, which in turn, keeps the brake fluid from vibrating too much and causing bubbles. Therefore making the brake spongy. 

Quote from: Kijona on January 01, 2012, 04:41:02 AM
When you say "spongy" do you mean that when you squeeze the lever, if you don't squeeze it fast enough, you'll get all the way to the end of its travel with little/no braking?

I could cry.....I really could 

Quote from: Dizzledan on January 02, 2012, 03:35:05 PM

Quote from: mister on January 01, 2012, 11:01:27 PM
I think the problem is a lack of milk in the handlebars 

Michael

A lot of people never understand this theory. It's not just plain old 2% milk that is required, its evaporated milk. The dry white substance helps balance the handlebars, which in turn, keeps the brake fluid from vibrating too much and causing bubbles. Therefore making the brake spongy. 

Damn and all this time I was using full cream