Brake Bleeding Gone Bad :(

[GhostofSilverider]

I have had this 91 KDX 250 for a few months and it keeps giving me problems. This time I needed to bleed the front brake which wasn't functioning very well, besides the fluid obviously needed to be changed. When I opened the master cylinder, the fluid had a coffee like color , and when I bled the caliper, hardly anything would come out, I emptied the master cylinder, cleaned the dirt at bottom and refilled with old unsealed fluid and after a while following the bleeding procedure I read about in a magazine, I managed to get a few ounces of dirty fluid out, while the "new" fluid moved into the system.

Then I must have done something wrong or something broke down , I depressed the lever with no fluid in the master cylinder. From then there was no longer any resistance when depressing the lever, it was like it was full of air. Little bubbles would come out every time I used the lever, same at the bottom. But I kept trying to get the air out by pressing th elever and no improvement whatsoever. I can't bleed the line anymore , when I use the lever , with the bleeding valve open hardly anything comes out .

What happened ? How do I get it to work properly ? It doesn't need to be like new but at least it has to stop the bike .

 

[dirt bike dave]

It is likely you have a very large bubble in the curve of the hose.

My recommendation is to remove the front brake system from the bike as a unit (master cylinder, hose, slave cylinder), and hang on a wall for a day or so. Tap the hose a few times with a screwdriver handle to knock the bubbles loose from the walls of the hose.

The bubbles will rise to the high end, and then you can bleed them out off of the bike (either through the master cylinder or using the bleeder on the slave cylinder).

I've used this method on the last two used KDX's I bought, including a '91 250. When I bought them, both bikes had very spongy front brakes that would not be fixed with normal bleeding.

FWIW, some people will tell you to buy a vacuum bleeder to suck the bubble out. I think you can get rid of it by hanging it on a wall.

BTW, if you have not bought new fluid yet, Motul 600 is great stuff. I used to overheat back brakes with stock Kawi fluid, but never a problem with the Motul 600.

 

[pesky nz]

the quickest way is to push your pistons back into the caliper by easing your disc pads appart, 2 tyre levers do a good job. This will force fluid back into all the right places and you can carry on as you were. After you have finished you can lean the bike over to the left so that the brake hose is up hill all the way to the master cylinder (and with a full master cylinder) squeeze in the lever and tie it in for a couple of hours. When you release the lever the last tiny air bubbles enter the reservior and you can then overflow it and fit the cap to finish off. This will stop air getting in the line if you take a spill while riding. Wash down with lots of water to neutralise the brake fluids paint stripper effect before tying lever and after overflowing reservior

 

[sr5bidder]

I use a syring and a hose (or hoses) to connect the syring to the caliper and bleed it backwards by pushing fluid in from the caliper up to the cylinder....with it comes all the air.

 

[mudpack]

I use a syring and a hose (or hoses) to connect the syring to the caliper and bleed it backwards by pushing fluid in from the caliper up to the cylinder....with it comes all the air.

:cool: Reverse bleeding works well on motorcycles.

 

[Bonehead]

If you don't have a big syringe go grab the turkey baster from the kitchen Add a piece of gas line on it and Bam your reverse bleeding. Add a zip tye around the squeeze bulb it wants to pop off if you have to squeeze real hard Then deny that the turkey baster in the garage is the one from the house

 

[sr5bidder]

works real well for the clutch slave cylinder found on those nasty orange bikes too!

 

[motopsycho87]

I have found with my kdx, lean it over (with the reservoir full and lid secured) so that the resevoir is at the highest point, then keep flicking the lever over and over and over. The air eventually makes its way to the resevoir, keep refilling and flicking until you get a firm lever! Works for me.