my brakes are horrible where to start??

[bradshaw106]

I have a 79 xs with discs front and rear. How do I get my bike to stop again? You can mash on the pedals and the bike will slow, but If I had to do an emergency stop i would be dead.
I put new pads in the rear but that did nothing. I don't even know where to begin. I was thinking updated master cylinders??

[slow rider]

You should get the front ones working first, they are important. Does the lever pull in all the way to the handgrip or does it stop halfway? If it stops before it reaches the handgrip, the piston in the caliper may be seized or the bolt with the rubber cover at the caliper may need freeing up. If the lever pulls all the way to the handgrip you have air, a leak, bad master cylinder, or something else bad.

[dogbunny]

Since my brakes also are horrible, I'll be watching this thread.
I know brakes. I have a new master cylinder, lever, brake line and fluid in the front, only the caliper, disc and pads are original. Everything works just fine, the line has been bled, except the stopping power is way weak. The only thing I can think of is that the pads are glazed. Pad thickness is okay, I have not looked at the surfaces.
I've ridden another XS650, so I know my brakes are not normal.
The rear brake also sucks, once again, everything is there and working, but in my case the rear is a drum. Once again, I'm thinking glazed shoes?

[bradshaw106]

My bike sat for a long time. when I got it flushed the brake fluid front and rear and bled the systems. To the best of my knowledge I have full travel of both front and rear levers. defiantly feels spongy in the front but I bled the air...... maybe an updated master cylider
could be just old. Im hoping it's not my rotors I heard you cant turn them.

[slow rider]

yfrog.com/5cimag0191jj yfrog.com/jvimag0195j One side of the caliper moves on the bush under the rubber, when the piston pushes on the disc it draws the other side on to the disc. If the bush is not able to move inside the rubber it wont let the two pads clamp on the disc. It needs to be clean and at least have some wd40 on it. The pictures are a left side brake.

[pamcopete]

bradshaw106,

Bleeding the brakes on the XS650 is one of the real challenges that we all have to master. It's almost like a right of passage. If you get it right, you can tell the tale to all your motorcycle buddies over a cold beer.

1. The conventional bleeding method is just a starter, so do that first.
2. The results from #1 will not be satisfactory. The lever will still be spongy no matter how long you try.
3. Try removing the caliper. Turn it so the piston is facing the floor. Alternatively press the piston into the caliper (very gently)followed by gently pumping the lever to push the piston back out. Watch for the air bubbles in the reservoir. Do this until your arms hurt.
4. Or...get a vacuum pump type bleeder and suck the fluid and all the air bubbles out while continuously adding fluid to keep the reservoir full..

[grizld1]

A couple of things to note here. When lubing the bushing under the rubber sleeve, use disc brake lubricant, and be sure the sleeve is still flexible. If it's lost flexibility, replace it. If you're deglazing pads, use a piece of medium garnet paper (woodworking sandpaper) or medium Scotchbrite (the type for use with metals) taped down on a known-flat surface such as a bit of plate glass. Move the pad on it in a figure 8. Don't use wet-or-dry paper, as it'll leave metallic residue. Use the same abrasives on the rotor, wiping down with acetone as you work. Then do a fresh break-in on the components. It take very little to deglaze pads, and the rotor cleanup should be done whenever new pads are installed. Breaking glaze on a rotor is another story. It can be done by hand if you have a couple of days to devote to it, but replacement is a more practical idea. If you know what you're doing rotor glaze can be broken with a ball hone.

Re. lines, the longest manufacturer's service interval I know of for rubber lines is 4 years. Flexing lines yield mushy action. Braided stainless lines last indefinitely and don't flex.

Re. bleeding, unscrew the brake line junction block from the lower clamp so that you can tweak it closer to the vertical and allow air to rise out of it instead of being trapped, and reposition the master cylinder assembly and turn the bars so that the cylinder is angled a bit upward toward the reservoir, allowing air to rise. Remove the MC top, pump the lever till you see not bubbles rising, give the line a few wiggles, replace the cap, tie back the lever, and go away for a few hours. Repeat if needed. When you have pressure, attach a piece of clear vinyl hose to the bleeder valve on the caliper, and run the hose into a bottle. Apply light pressure to the brake lever, at the same time opening the valve just enough for the pressure to release. Close the valve just before the lever bottoms. Keep an eye on fluid level in the MC. This is a fine opportunity to replace the old fluid.

With the OEM floating caliper, using an 11 mm. MC will provide more force per pound of pull than the OEM 14 m.; not recommended for use with rubber line. Ferodo Platinum pads are a big improvement over OEM. Following Michael Morse's advice, I'm currently using a pair of his Vesrah sintered pads. Rotors won't last forever with those, but they're very effective.

[jamesgs4]

also make sure your front pads arent contaminated with oil. a leaky fork seal could easily ruin them, making them feel "wooden"