firm brakes

just a thought, maybe you have a faulty brake master cylinder.

 

I would also lean towards adjusting the cables maybe

 

Hi Larry,

Check to see if you have clearance between the clutch lever and the master cylinder where the two touch. This can be adjusted with the screw that actually touches and pushes in the master cylinder piston. I once had the front lock up and this was the problem, lucky I wasn't to far from home. Best of luck.

 

So your saying that the lever doesn't travel as far as you want it to?
That's the complete opposite of what most riders complain about but ok.

Chances are there may have been air or other impurities in your brake lines or caliper for a while which will give you a softer feel on the lever and less clamping and therefore braking force. Air has a habit of rising to the top of a system especially whilst its under pressure, so chances are it's taken a while for all those little air bubbles in your caliper to make their way up to the master cylinder and then up into the reservoir. Once this has happened there's only brake fluid in the system (as IMHO i should be!) which will give the lever a nice firm feel and also give more braking force.

I'm not saying that a brake lever should be an ON/OFF switch as that indeed would be dangerous, but it shouldn't be the distance the lever travels which determines how much braking force is applied, its the amount of force you apply to the lever!

If you try very lightly using the brake lever do you get very light braking?
If you gently squeeze the lever tighter does the braking force increase?
If you quickly grip the lever does the front wheel lock up?
If yes to all of the above, it's working fine. If there's a no in there then there may be other issues that haven't come to light yet.

Other things that may be causing non-consistant braking force would be a worn master cylinder or sticking pistons in the calipers.
When you replaced the brake pads, i assume you depressed the pistons back into the caliper slightly to allow for the fresh pads. How hard was it to push them back in? One thumb light/medium pressure, two thumbs firmly, or assisted with a G-clamp/power of christ compels you?

Oh, also if there was air/impurities in the system then putting in new pads would have stiffened up lever travel as it reduces the amount of brake fluid/air/water in the system that needs compressing in order to get the piston to push the brake pad and clamp onto the rotor.

Hope that answer will be of some help to you. If not just give me a shout and i'll keep on churning out suggestions. <!-- s:lol: --><img src="{SMILIES_PATH}/icon_lol.gif" alt=":lol:" title="Laughing" /><!-- s:lol: -->

PS. I'm going to assume you know about the position adjustment knob on top of the brake lever. It should have 4 or 5 numbers (1-4 or so) with the different numbers giving the lever a different 'mid-point' for your brake travel.

 

... and there's the tid bit of info that answers everything. <!-- s --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt="" title="Very Happy" /><!-- s -->
By the sounds of it you need to give your calipers a bit of an overhaul. You should be able to do this in about and hour or two depending on how stuck and stubborn the pistons actually are.

In the service manuals they'll tell you that you need an air compressor to get the caliper pistons out but as i don't have an air compressor at home i do it my way. I'll take you back to a frustrating time when i had my FZR250 and was faced with a similar situation you were. Whilst riding along one night i smelt a rather familiar smell, cooked brake pad; so i stopped to inspect all of my rotors and see what the culprit was. Turns out that one of my front rotors was hot enough to burn the pads of my thumb and forefinger so i found the culprit pretty quick, with a few obscenities thrown in for good measure.

If you take off both the calipers and drain the of brake fluid then we can get right down to business. You can either use those cans of brake cleaner (recommended) or you can just use brake fluid (nasty). Give them a thorough clean then start to remove the pistons one by one. As you pull a piston out you'll see two rubber rings; take very very good care of them and keep them with their matching piston.
Now once you've (eventually!) got all the pistons out give the entire caliper a really thorough clean, then onto the pistons. They need to be absolutely immaculate, so don't stop cleaning till they are. I use one of those green dish scourer things you can get from the supermarket as with a bit of effort it should remove all the grit & grime without scarring/scoring the piston.
Once they're all immaculately clean or as close to it as you can get before your fingers bleed, it's time to reassemble. Make sure you know which one the dust seal and the inner seal is and don't get them mixed up! If any of the seals are broken, brittle or just generally manky then it's probably a good idea to get a caliper reconditioning kit which aren't cheap but are worth it if you like properly working brakes.

Once you've put the calipers back together it's time to put them back on the bike and fill the system. For a dry start (no fluid in the system) i personally prefer filling from the bottom up with a jumbo syringe attached to the bleed nipple using the same hose you use to bleed the system. Once you've filled the system then it's time to bleed it thoroughly the conventional way. Some people recommend squeezing the brake lever overnight to pressurise the system and force out all the bubbles; i've never done it but some people swear by it. I personally just make sure i bleed the system again after a few rides.

 

Hi Larry & Koma,

Koma loved the bit about refilling the brake system from the bottom up. I have a yamaha sr500 and am having all sorts of problems getting a firm brake. New master cylinder kit and brake caliper kit and still no difference. Will try filling from the bottom up, I think this is how they do it at the factory.

Larry there is a clutch cable on ebay for $26 I think, not sure how much yamaha want for them but now you have a ball park figure. Although they can be repaired. To explain my last post a bit better. Connected to the clutch lever there is a screw that pushes on the master cylinder when you pull the lever in. Make sure there is free play between this screw and the master cylinder. Although the previous owner of my bike had balance problems and the clutch lever and master cylinder could be off of a totally different bike. On the master cylinder smear a thin layer of rubber grease on the pistons where they rub up against the rubber rings in the brake caliper. And best of luck.

 

Good to hear you got it sorted.
Most of the time brake issues are easily sorted with a flush, a clean or both.

 

Hi guys, Im currently trying (and learning) to overhaul my brake calipers on my parts bike, which i will then tranfer into my running FZR.
Ive got the Caliper off and sitting on my bench i two halves. But I cannot pull those pistons out. do you have any tips or should i take both halves to a mechanic friend to have him shoot air into it?
Thanks very much and happy riding.

 

Did you split the caliper in half?? <!-- s:-? --><img src="{SMILIES_PATH}/icon_Eyecrazy.gif" alt=":-?" title="Eye Crazy" /><!-- s:-? --> Without doing that you can use compressed air to get one piston out at a time if you make a clamp bar to hold the other one in. They shoot out pretty fast though. So put some cloth in there to catch the piston, not your fingers.

 

Found an old post of mine

I took my original set of calipers to work and removed the pistons one at a time.

To get one piston out I put a bit of 20mm thick wood beween two opposing pistons and put a home made clamp around one of the other free pistons. This leaves one piston free to pop out.

The clamp consists of two bits of 25x3mm flat steel bar about 100mm long with a hole at each end and a couple of 1/4" (6mm) bolts 2" (50mm) long. When done up tight, this leaves enough room for the opposing piston to come out.

I then applied compressed air to the hose connection. Also wrap the caliper in rag as the piston comes out very fast, with a fair bit of noise and vapourised brake fluid. WATCH YOUR FINGERS!

As the pistons were dirty looking, I easily cleaned them up to a lovely shine with scotch-brite scouring pad. I also cleaned out the cylinders (without removing the seals) with a clean rag.

I applied brake fluid to each piston and and seals and refitted the pistons

 

Haha yeah its in two halves, not sure about 2KR but 3LN calipers are bolted together. I'm taking the time to give them a good clean because they are my spare brakes and i can make them perfect before i transplant them over to my running FZR. Once I sort out these brakes and have the forks re oiled/sealed, Everything on the bike should be 100% - Great feeling