front brake problem

[gerwintown]

Messing with the GS550 lately, getting it ready to hit the road within the next couple of weeks, I noticed that when I pull the front brake level, not only does it feel spongy, but it sounds spongy as well. I know spongy brakes can mean a couple things, like air in the lines, need for new hoses, need for rebuild of Master cylinger, etc. Is the sound Im hearing just apart of the "spongy" symptom commonly described, or does it point to something more specific, like the definite need for a M/C rebuild? The brake lever definitely feels like its pressing against a dry piece of rubber or something, and is making a squeeky/spongy sound right at the lever. It feels broken. The brake fluid is at the correct level. I have no idea if im getting movement or pressure applied on the brake pads as it is on its center stand on my back patio and wont be moving till i finish painting the tank. So what say ye? Should I try bleeding the system? Go ahead and order a rebuild kit? Any help will be very appreciated.

[etravis2]

Bleeding the brakes can tell you a lot about how the brakes are working and is easy to do on a motorcycle. I would start with that. Then check both sides of the M/C for any dampness. Mine leaked at the lever. Pull the boot off the other side to check the metal fittings.

[hampshirehog]

I think on your model you've got a rubber boot in the master cylinder, lever end on the plunger arm. These can split / perish and squash over to the head of the plunger arm and you might be squeezing the lever against this. alternatively it might just have gone dry and hard or got a bit of muck in there. Easy check - whip the lever of and have a look. That rubber isn't strictly all that important - it's a cover to stop muck and rot getting in so you can get by without it as long as you maint is good and you keep it clean.

If your brakes are working, you should be able to see your caliper move slightly as it's a floating design. (you only apply pressure to the outside pad and the caliper moves over to equalise pressure against the inside pad)

[chuckycheese]

Mine, as well.

I know EXACTLY what you mean when you say it sounds spongy; my GS1100 does the same thing but my GS750 doesn't do it at all. Hopefully, someone will know exactly what's causing it.

[Steve]

Do a couple things first. Evaluate the total situation.
How long have you had the bike?
Can you remember when the last time the brake fluid was changed?

If you have recently acquired the bike, it's best to change the fluid, anyway, but here is a good way to tell how long the fluid has been in there ... look at the color. If it is clear, or close to it, it's probably good. If it's the color of root beer, it should have been changed a year ago.

One reason the fluid changes color is because of the moisture that is in there. Brake fluid attracts moisture, and increased water in the brake fluid reduces its effectiveness by lowering the boiling point. Brakes get rather hot when used, and the moisture in the brake fluid can turn to steam. The steam expands, but is compressible, giving a very mushy feel to the brakes, reducing their effectiveness the most right about the time you really need them, like going down a good-sized mountain. New fluid also operates more smoothly, and that might be part of your problem.

I would start by flushing the system, including taking the master cylinder apart and cleaning all the rubber parts with fresh brake fluid and inspecting them. If anything looks not quite right, replace it. After all, brakes are not merely a convenience. Master cylinder kits are not expensive, and you won't have to worry about getting another one for another 20-25 years.

.

[XL-erate]

Hard to add to the good info Steve posted, but in addition: brake fluid wicks moisture from the air even though it's supposed to be a sealed system. Those heat/cold cycles he speaks of result in condensation events in brake parts. The water indeed boils at the caliper and that's the main place it's drawn in when caliper cools. The squeaking sounds are often due to the water content setting up corrosion in the aluminum pistons and piston bores of both the master and caliper.

Dpending on local weather conditions I like to change the hydraulic brake rubbers at least every 18 months, inspect every 9-12, more in severe conditions. Cheap insurance.

Also a spongy brake can be due to a weakened rubber brake line. Surprising what a big difference the balooning effect of a weak line can make. I inspect those at least every 6 months, at the least looking for signs of cracks or degradation.

[Nessism]

To expand on what Steve said, if the brake fluid is dark I recommend a total system tear down. The fluid starts to solidify after a few years and scale develops on the inside of the parts – including the brake line. Suzuki recommends replacing the brake lines every two years, so if yours are 25 years old, it’s time. When disassembling the system you will find chunks of jello like material that should be cleaned out. Flushing the system by bleeding will not get all this stuff out of the system. Taking the caliper and master apart is fairly easy. If the rubber parts are in good shape you can reuse them (except for the brake line). Most likely the boot on the master cylinder will be torn and require replacement. I recommend using the Suzuki factory parts – I’ve had poor experiences with the K&L brake system parts Z1 Enterprises sells, although I like Z1 for the most part.

Good luck.

[gerwintown]

hey thanks, yeah....the color of the fluid is root beer colored, and i bought the bike a year ago and all i did was check the level. so ill follow the advice i received here and flush the system with new fluid, after taking apart the master cylinder to see if everything looks okay. i found a rebuild kit online for 24 dollars (local dealer wanted 50 and still had to order it....good luck with all that guys), but obviously ill get in there and check it out first. okay well you all have been very helpful, ill update when ive either fixed it or reached the next step, thanks.

[Dogma]

What do people do with the old fluid? Dump it in the oil change tub and haul it to Auto Zone at the next oil change?

[Steve]

There is supposed to be nothing but motor oil in the stuff you take to Auto Zone for recycling, but I'm sure we would not be very surprised to find many other chemicals in the mix.

.

[XL-erate]

I believe it's non-petroleum derived ethylene glycol of it's DOT 3 or 4. Might be good to have an EPA Certified Toxic Spill HazMat crew on standby while bleeding. But be careful because they may take the bike for evidence if any spills on the ground.

[chuckycheese]

Noise

This is all great maintenance information but......what's causing the noise? (I doubt it's dirty brake fluid; mine's clean...and has a 'squishy' noise, too.)

[gerwintown]

^^^ yeah thats what im interested finding out as well. the spongy feel is commonly reported but i never see any mention of squishy sound.

[KRISTI'SGS550]

This is all great maintenance information but......what's causing the noise? (I doubt it's dirty brake fluid; mine's clean...and has a 'squishy' noise, too.)

Did you check the rubber cap in the M/C? I bet it is making the squishy sound.

Cory

[bwringer]

Put a wee spot 'o grease on the part of the lever that contacts the piston.

That should get rid of the noise and improve the feel considerably. It's worked for me several times, anyway.

This part of the lever has to slide across the piston slightly as it pivots. If it's completely dry, you get a tiny noise and an odd, notchy feeling.