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Well I have a good front break but I'm not sure where to start on the back. I have bled the rear but it hasn't helped (I haven't seen any air bubbles). When I press the break pedal it will barely slow down and to get it to do that I have to press very hard. Where would be the first place to look or rebuild?

Vinny


Oh yeah. I'ts a '93 KDX200.

Actually I always had problems with the rear brake locking instantly. It was always on or off.

Maybe you need to adjust the actuator bolt? It might need to be ran down a little, so it starts working sooner. Know what im talking about? Im sure u checked the fluid? Pads?

It's got new pads and I did a fluid transfusion I guess you could say. When I first put the rear break back on I could pump them up but it lost pressure in just a minute or so. Now I can't pump it up anymore

I'm assuming you have bleed the rear brake correctly. You may want to try reverse bleeding from the cailiper to the master cylinder to drive out any trapped air prior to breaking open the brake system. If you have flushed fresh fluid through the system and have tried reverse bleeding then it sounds like you need to pull apart the master cylinder and clean it up and check it out. May need to be rebuilt.

FWIW - If your brake pads were very worn and you did not clean the caliper piston prior to shoving the piston back into the caliper there may be a problem there. On a caliper however, the piston when it has problems sealing usually leaks fluid (or will not retract due to crud or corrison) after applying the brakes. Therefore, I believe you likely have a rear brake master cylinder problem.

How do you reverse bleed it?

Pump it up and crack the line at the top where it goes into the master cyl. It makes more sense to me to do it like this all the time, just make sure you check your fluid level frequently while doing it as you will get air in the line alot faster. I would think you need a rebuild if it is not holding pressure but that is going by car master cylinders.

vinny wrote:How do you reverse bleed it?

"Reverse bleeding" is filling the brake system with fluid from the caliper. Usually done by using a syringe filled with brake fluid and a short section of appropriate clear tubing. (you want zero air in the tubing prior to starting the fill i.e. no need to push more air into the system) Remove the fluid reserve cap and watch for dirty fluid and air to be released into the reserve. Suck out the dirty fluid and repeat until clean fluid containing no air bubbles is filling the brake fluid reserve. You don't pump the brake lever during the process - pressure from the syringe will force brake fluid up the line through the master cylinder and into the fluid reserve. Sometimes this can be helpful to remove air or crude which has become trapped in the brake system.

I tryed reverse bleeding the rear break but there was no change. It was very hard to get the fluid to go in and I believe after it took some it wouldn't take any more. A couple more details I failed to mention that may be of some help. When I mash the break pedal it goes down an inch to an inch and a half (to far I believe) and it makes a swush sound. Any more help would be great!

Vinny

I've heard that sound....
Sounds like it might be time for a Master Cylinder rebuild.
Easy job, seal kit sells for ~$35.00, and should be readily available because so many different bikes use that Master Cylinder.
The toughest part of the job is getting the circlip out where the plunger goes up into the cylinder. 11 minutes bench time.