Posts
79
Joined
2/4/2015
Location
CA
Edited Date/Time
5/13/2016 12:10pm
Disclaimer: I know this is a common topic but many of the threads are dead ends.
Rebuilt my '03 CR250 over the winter which included new pads and rotors. While the front brake grabs, it is super spongy. Once it's 'biting' the rotor I can still pull the lever past that point and almost to the bar.
I've gone through all of the common trouble shooting methods including;
Bleed, and bleed again, and again...
master cylinder rebuild kit
zip-tie the lever and leave it for a few hours
put on a braided line
O/S rotor
rotors and pads are clean and free of any contamination
The only item left that could be the culprit is the caliper... is it possible that when pushing the pistons back in when changing the pads something like a seal blew?
Any advice would be greatly appreciated. Thanks!
Rebuilt my '03 CR250 over the winter which included new pads and rotors. While the front brake grabs, it is super spongy. Once it's 'biting' the rotor I can still pull the lever past that point and almost to the bar.
I've gone through all of the common trouble shooting methods including;
Bleed, and bleed again, and again...
master cylinder rebuild kit
zip-tie the lever and leave it for a few hours
put on a braided line
O/S rotor
rotors and pads are clean and free of any contamination
The only item left that could be the culprit is the caliper... is it possible that when pushing the pistons back in when changing the pads something like a seal blew?
Any advice would be greatly appreciated. Thanks!
Grab a friend, tell them to open bleeder - you pull lever in (hold it), ask said friend to tighten bleeder - you: release the lever. Repeat while adding fluid to master, do this about 5 times, keeping the master topped. Tighten bleeder and see if any improvement exists.
Continue adding fluid to reservoir to eliminate air entrance, and push all the air out in 1 direction. For me its been generally a fail proof method to eliminating sponge and enhancing brake strength.
I'm going to try putting the master cyl from another bike on that I know is good, and see how it feels with my caliper, and put my master on the other bike and see how that behaves.
Hopefully this will be able to pin point then if the problem is the MC or caliper.
*fingers crossed I can narrow it down to the caliper and just rebuild that. Although it does not leak, like 809 has mentioned.
The Shop
Next go out and bed in the pads.
Also, I think you need to address your caliper. On a bike that old you might as well just rebuild it and make sure the pins are cleaned and greased and that the pistons do not have rust or pitting that is dragging on the seals.
And any dirt biker who plans to ride for any length of time should do themselves a huge favor and spend $25 - $30 for one of these. Worth its weight in gold. Especially if you own a bike with a hydraulic clutch.
1) Take the brake caliper and hose off of the bike (without disconnecting them from the system).
2) Have someone hold the lever in or put a wire tie on it to build some pressure.
3) Raise the caliper up so that the bleeder is the highest point in the entire brake system and the hose doesn't dip down below the master cylinder.
4) Open the bleeder and use something to compress the pistons all the way into the caliper. If you leave the brake pads in there, you can use something like a plastic Irwin Quick Grip to squeeze in the pistons. (Make sure you keep the bleeder pointing up and higher than the rest of the system.
5) Close the bleeder.
6) Make sure the reservoir is full of fluid before letting off of the lever.
7) Slide something about the thickness of your rotor between the brake pads. I use a motion-pro flat tire iron.
8) Pump the lever until the brake pads bite down on your "shim". (The caliper is still higher than the rest of the system).
9) Repeat steps 4, 5 and 6.
10) Bolt the caliper back on the fork lug and pump the brakes up to build pressure.
A vacuum bleeder helps and a setup that allows you to reverse bleed the brakes using pressure is also a great way to ensure the air is 100% removed.
Going to try the syringe method mb mentioned and p/u a caliper rebuild kit.
Yeah, the braided lines I got came with new banjos and washers.
To all the guys saying there is still probably air trapped in the lines; even though when cracking the bleeder during a normal bleed procedure and there's no more air coming out just fluid, there can still be air trapped?
Paw Paw
Pit Row
Leave the caliper mounted? remove the pads? Then...
-I take a length of tubing that fits over the bleeder and place the other end in water. This keeps air from being drawn back into the caliper.
-Crack the bleeder just enough to let pressure out and start slowly pumping the brakes. If you use a clear container for the water and brake fluid, you can watch it come out of the tubing. Make sure the master stays full, it's easy to let it run low since the bleeding process is much quicker.
-Tighten the bleeder, remove the line.
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