One more IMPORTANT note.

When you do your brakes remember the caliper floats - it slides on pins to compensate as brake pads wear. Those pins can become crusty and corroded. ALWAYS clean and lube them with wheel bearing grease whenever you do anything with your brakes. The pins can be lightly sanded with wet/dry 600 or 1000 grit or steel wool, even polished with Flitz, to make them work properly. The calipers should slide freely on the pins. There are rubber boots to keep crud out of the pin area that need to be kept in good shape too. Replace them as needed.

A caliper not being able to slide on the pins freely can cause braking issues.

 

Ok, all done finally. I basically rebuilt the master cylinder and caliper without replacing the seals, but they look to be in great condition and are not leaking, and had hardly any gunk. I also greased up the caliper pins.

Before hooking up the caliper I filled it with fluid. I also bench bled the mc. I then hooked up the hose and reverse bled the brakes from the caliper nipple. I did this until the reservoir was full, emptied and repeated 4 times.

But, the lever is just as mushy and cannot get the brake lever hard. I could not get a vac bleeder but the reverse bleeding should do the trick. im about ready to give up and buy all new front brake set. Ill leave it zip tied overnight hoping that helps.

thanks

 

Your line must have a kink or bulge you are not seeing.
Buy a new brake line before you buy a brake.

 

One question and then one thought...

How did you do the reverse bleed?

Is it possible that the reverse bleed can leave air in the lines the way you did it?


A brake system is about the simplest hydraulic system possible. One piston pushing fluid through a hose to push another piston, in this case another two. No tricks, no gimmicks.

If the master cylinder is moving freely and pumping fluid, the brake line is not expanding under pressure, and the slave cylinders (caliper pistons) are moving freely when the fluid is pushed by the master cylinder the system is complete and working. The only hardware failure can be leakage and that would be quite visible or a bad line that is expanding under pressure. If the brake at one time was good the system has the capability to perform as good as before.

If the system hardware is good but the braking is soft, not being able to experience the kind of softness, I would say there are only two things that can cause this.

1. The brake pads are contaminated and lost the friction coefficient to do the job.
2. There is an air pocket in the fluid in the system.

A kink in a brake hose that would restrict or stop flow would actually make the lever pull hard without equal braking action, because you would be forcing the fluid past the restriction. It would not be soft. The restriction would slow or stop fluid flow which would result in high effort lever travel. Plus once the fluid flow was complete to get pressure to the pads and squeeze the rotor the brake would be strong, not spongy. Once the fluid has flowed if there was no air in the system the pressure would be equal through out the system as if the kink never existed. Think about it.

 

I bench bled the mc, then I filled the caliper using a syringe and clear tube before connecting the brake hose. I made sure the banjo bolt hole was the highest part of the caliper, then when full without moving it I had someone else hook up the banjo bolt. Then I emptied the reservoir and filled from the caliper nipple making sure only fluid got in. I always started pressing in the syringe a bit before opening the nipple. The first time I opened the nipple some bubbles came out into the clear tube and moved up the tube. As soon as the bubbles stopped I closed the nipple and made sure the tube was clear of bubbles then started again. Once the reservoir was nearly full I always closed the nipple before the suction stopped. Then I emptied the reservoir, filled the tube and started again. I did this 4-5 times. Only got bubbles out of the reservoir the first 2 times.

I zip tied it thru all last night and this morning it feels real firm, nearly as hard as before, but just sitting there. I have to test ride it, I'll let you know how it goes.

Im thinking maybe the mc seal may not be at 100%, or the pads may be bad as you said. Could that be caused by driving in dirty city street rain puddles? They are nissin pads so maybe they are the original pads. I guess the best thing to do is replace the hose, mc seals, caliper piston seals, pads and pins all while im at it.

Thanks max and klx

 

Well, after zip tying the brake for 48 hours the brakes are working properly no, as firm as ever and braking as good as ever. I hope it lasts more than a week this time. That would also leave me more cash for other mods. Ill let you guys know.

Thanks for all of your help!

 

Good stuff!

 

Well, back to it again. Rode it this morning to work and the lever was maybe at 80%, thought maybe it was because of the cold. Rode it to the bank at lunch time and it was maybe at 60% and wont lock up anymore.

Im already planning on replacing the MC and Caliper seals and the hose, but just out of curiosity, what could be causing this? It has no leaks at all, zero, not even a drop. The hose does not swell anywhere. I thought maybe the pads but that wouldn't cause the soft lever, just reduced braking power.

Cheers

 

Zip tied it last night and the brakes are real firm this morning. Weird. Im looking for the rebuild kits locally.