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I think I have a problem master cylinder or caliper front brake.

The front brake won't bleed right. I know how, I've done many. This one seems very weak; I can pull the lever all the way in to the grip. It will pump up pressure though. Sit a few seconds and it's mushy again. New brake line; stainless steel braided in fact. That's what got me going on this.

So, I think some seal is leaking but once pumped up, she holds!! It behaves just like a little air is in the system. I even took it all off the bike and bled it on the bench.

Anyone with this experiance? I don't know wether to change the master or caliper and don't wanna do either; costs and all.

BTW rear brake with new Stainless steel line and hand operated, so it's a longer line than the front. It bled perfect first try. No mush, full lock with only a 1" of lever movement.

I had the same symptoms on another bike. It was the master cylinder leaking back into itself. I got an new one cuz it was before ebay. If it were the caliper there would be a leak past the o-ring on the piston.

I guess you tapped the line to work the bubbles out while bleeding? I have two or three complete front brakes for a KX. PM me with your address I will send one to you, if you are in the need for one, just pay for shipping is all I ask. oh yes they work. I just seem to have collected a few.

I would attempt to back flush it from the caliper to the master cylinder. I agree it is very likely the master cylinder and back flushing with brake fluid from the caliper to the master cylinder may free up the little valve at the outlet from the master cylinder.

I did back flush it. In fact, I power flushed it with a little help from my air compressor!! Ha!!

I do notice that there is some back pressure into the master. When I pump the hand brake, I can see a mound of brake fluid pushing up through the reservoir of fluid in the master. Each pump of the handle, a little mound of fluid. I think that is brake fluid being forced back into the master resivoir instead of being forced down the brake line.

Krazyinski: Thanks!! I'll PM you.

I've had this problem before on a 1997 kx125. I ordered a piston comp brake from bike bandit. it is in the front brake master cylinder schematic. Thats what they call it. It fixed the problem

Thanks for the tip henry954!!! I think Krazyinski is sending me a set-up. If not, then I'll order that part and give it a go!!

Shipped the entire brake assembly Tues parcel post left the line and caliper on didnt want any oil leaking or seals drying out. Its a working 2003 brake.

This way when you put it all together you know for sure its air in the line and not a bad master cylinder. shipping was not enough to worry about.

Just pass on the Holiday cheer!


Your welcome,

Matt

Thanks Matt!!
I am sending that Stainless Steel rear brake line your way. If you can use it, great!! It sure looks pretty anyway.
The guys on KDXrider are awesome and that's why I hang here even though I no longer have a KDX.

BTW, I was in San Antonio a year or so ago on business. Drank beer at some UFO place? Ate the best BBQ I've ever had out of town towards some hills? It was cafeteria style serving and tables outdoors. And then did the River thing late at night, ended up in some night club upstairs with a great piano player banging out some tunes. I'm bad at remembering names, but it sure was a good time!! It was Harris/Farinon Microwave where I was involved with acceptance testing new digital microwave gear. Last time I was in San Antone was my basic training at Lackland AFB, 1973?!?!? Ha!!

Rudys BBQ, @ Boerne Stage rd off I 10 sounds like the spot you described and is indeed some of the best, they have been there so long a fella could eat the cutting board and never know its wood.

If your ever in this neck of the woods I take you down to my ranch, Motorcycle ranch that is, (OK! a few cows,pig,coyote,deer and other wild animals ) they basically stay out of the way. Small but fun 400 acres on the San Antonio river, its been dirt bike only there sense the 70's. nick named the place of a thousand trails wouldn't think you could get lost on 400 acres but you can here.

I will take you up on that offer!! Next week, I'll talk to our engineering staff to see when we are expecting to order our next microwave system and that I want on-board with the factory acceptance testing. They may have a coronary to hear that I volunteer for anything, but I am sure to go since they usually have to force the Telecommunications Techs to go anyway.

Yup! Rudys was the name. I had a hard time deciding what I wanted to eat, they had so many choices of meats and sides.

And if you ever get out to California, the offer is extended to you as well: stay (and ski!!) at the Heitman Mountain Chalet!! Ha!!

Other things NOT being screwed up (misplaced backing plate for one)...what bradf said. What you described is exactly what you get with a bad piston seal on an MC. I just replaced one on my Honda.

RE: 'Mounds' of fluid. Normal. The seal that pushes the fluid sits 'behind' the feed hole so it can get a 'gulp' of fluid to push. Just before it seals in the bore, whatever is TRYING to be pushed just 'mounds' back into the res.

As long as it is indeed 'mounds'. There should be NO almond joy refluxed into the MC.

Mine mounds, - the coconut . . .