[SOLVED] Classic front brake issue?

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Charles
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Re: Classic front brake issue?

Post by Charles »

Yes, first thing I did was rebuilding the master cylinder. When I'll do the swap I'll check it again.
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Re: Classic front brake issue?

Post by Goofaroo »

Charles wrote: 05:03 pm Jun 06 2021 Yes, first thing I did was rebuilding the master cylinder. When I'll do the swap I'll check it again.
If it was assembled incorrectly that would definitely account for your problem.
Charles
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Re: Classic front brake issue?

Post by Charles »

Tonight I disassembled the master again. Nothing found. Return hole not obstructed, seals seems to be correctly installed.

I tried swapping the master with the sport one but the banjo bolt threads don't match, and it's a double on the sports.
Tomorrow I'll try swapping with the wife's husqvarna master.

I'm starting to loose temper on that brake.
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Goofaroo
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Re: Classic front brake issue?

Post by Goofaroo »

It appears to be assembled correctly. Is the bore pitted or corroded?

I would lube the bore and the cups with brake fluid and carefully reassemble it. You can bench bleed it a bit by putting some fluid into the reservoir. Work the plunger a bit until it shoots out of where the hose hooks up. You may have to hold your finger over the output to help it prime and create pressure. Then hook it up and do a vacuum bleed on it if you can. See if you get a different result.

If it still isn’t working, leave the cover on and the hose and lever but remove it from the bars and hold it up as high as the hose will allow. Pump the lever and take a screwdriver handle and tap on the brake hose from bottom to top and back down. Try the lever again. Repeat if needed. You’re trying to dislodge any air bubbles and get them to float up to the reservoir.

I hope that helps. If not there’s another idea you might try. Let us know.
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Re: Classic front brake issue?

Post by Goofaroo »

It would also be worthwhile to verify that your brake pads are seated properly in the caliper. I’ve had bikes come to my shop with the same symptoms you’re having. Spongy lever and no braking power. All fixed because the piston side pads weren’t seated properly.

Just a thought.
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Re: Classic front brake issue?

Post by KDXGarage »

OK, did a little clean up on this thread. If someone has a unique question, please make a new thread about his unique issue.
PRETTY PLEASE, let this be a thread about Charles brake issue. Thank you.
Thank you for participating on kdxrider.net. :bravo:
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Charles
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Re: Classic front brake issue?

Post by Charles »

Goofaroo, I tried your technique but found no improvement. I removed the caliper and the master so I hung the system vertical, with the line straight.

I inspected the bore of the master before reassembly and found no defect.

I double checked the caliper and took some pics. It appears to me that the pads are correctly installed but I could be wrong. Pins are smooth, pad spring is doing its job.

It's crazy being in so much trouble on such a simple hydraulic system
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Goofaroo
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Re: Classic front brake issue?

Post by Goofaroo »

Have you pulled out all of your hair yet? lol

The solution is right in front of you but sometimes a simple job can turn into a three ring **** show.

If you haven’t already it would be worth a shot to clamp the lever to the bar. Pump the lever and get it as firm as you can and then put a spring clamp on it and leave it overnight. With it clamped you can also beat on the hose with the screwdriver to try to dislodge the trapped air.
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Re: Classic front brake issue?

Post by DonnyV »

I'm no pro but I had the same issue as you, what I finally did was stopped bleeding at the bleed screw and bled at the bottom banjo then the banjo at the master. Just make sure you have brake cleaner and rags and clean up any oil, had to do this on the front and back brakes
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Charles
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Re: Classic front brake issue?

Post by Charles »

Hey guys,

After a "son positive to covid" break,followed by a "my wife broke her gearbox" break, then a "I crashed my KDX like an idiot" break, and a summer break, I'm back at working at it.

A friend of mine is coming at the end of the week, to help me bleed it. maybe fresh eyes will help.

I'll keep you posted.
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Re: Classic front brake issue?

Post by cbittner72 »

Had a similar experience and while I’ve got a KX front end, I believe it’s the same caliper. After reading various sources, it seems the master cylinder may just be weaker than other brands and newer versions. What I did is replaced the stock KDX master with one from an ‘05 KXF 250 off eBay. I rebuilt that plus added a Galfer SS line with CR routing. The front will lock no problem now. This is a 1 finger brake that is very firm.
Charles
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Re: Classic front brake issue?

Post by Charles »

Thanks for the input.

If bleeding is not satisfactory, the next step will be to replace the parts but I'll wait, I'm on a tight budget and used parts are really expensive in my country.
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Re: Classic front brake issue?

Post by GATOROC »

I'm looking forward to hearing what fixes your issue. My 220 has always had a weak front brake, and that was really confirmed when I picked up the 200 and noticed the drastic difference. When I did the fork swap I tried the kx250 master cylinder, but it didn't change at all. Multiple bleeding attempts hasn't changed anything. I still need to make sure the caliper is working properly. Hopefully you get it figured out!
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Re: Classic front brake issue?

Post by TwistedRoot »

KDXGarage wrote: 11:08 am May 16 2021 25 year old dust seal and fluid seal may need to be replaced
This is a MUST do.
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Re: Classic front brake issue?

Post by MoonStomper »

I had similar issues, maybe not as bad. I swapped in a Russel Stainless Steel brake line that I bought from Fredette RP, and reverse bled it. Then used a car bleeder to put suction on at the caliper to make sure I pulled out any stuck bubbles out the bottom. Still not as touchy as my son’s KTM, but the bike stops really well now and no more spongey lever.
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Charles
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Re: Classic front brake issue?

Post by Charles »

Ok, so I tried again: coventional, reverse, syringe, banjo... It does not get any better. Something's wrong.

I guess I'm in for a caliper repair kit, a new braided steel hose and maybe a new master and disc. Just have to save a bit of money now.
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Re: Classic front brake issue?

Post by MoonStomper »

Replaced my front rotor with a new aftermarket one I got from FRP, installed fresh pads and bedded them in per instructions. Still haven’t installed the kit in my master cylinder, but the brake now feels very good. My old original rotor was pretty far out of spec. It makes sense that it could be your underlying issue combined with the old brake hose getting soft.
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Charles
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Re: Classic front brake issue?

Post by Charles »

Steel braided line, caliper repair kit and vacuum bleeder tool are finally on their way!

Used parts price are skyrocketing here so I'll try to avoid replacing the master cylinder. A decent used one is at least 80€, even from 10 to 15 years old bikes.
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Re: Classic front brake issue?

Post by KDXGarage »

Getting closer!
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Charles
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Re: Classic front brake issue?

Post by Charles »

Here we go again!

I installed the caliper repair kit, it was easy to do. Caliper was spotless, pistons, gaskets, everything was fine. I replaced the dust and fluid seals, cleaned the pistons and everything and rebuilt it.

Warning: For those who attempt to do it for the first time, be EXTRA CAREFUL if using compressed air to extract the pistons! It works really well, but it does eject them like 22 cal bullets, even while being gentle with the pressure.

I installed the steel braided line (HEL line, custom made by a serious shop). So basically where we're at:
-Master cylinder rebuilt
-Caliper rebuilt
-Steel braided teflon line with new banjo bolts and gaskets

I started the bleeding like so:
-Reverse filled the circuit with a syringe, tapping the line
-Primed the master and bled "traditionnaly" a few times
-Then I went to the vacuum tool bleeding for quite a long time and....

Still the same problem. Then I got angry. It feels like there's no air in the circuit and somehow I'm lacking range, as soon as the pressure builds up I'm crushing my fingers between the lever and the handle.
I then decided to remove the heat-shrinkable sleeve that was on the lever since I got the bike, as it is at least 3-4mm thick. Maybe that would help?

Guess what? It was hiding a broken lever just holding with a piece of copper tube hammered on it!!! Man!! I've been riding it like that for four years! I'm quite ashamed that I never checked it... So maybe all of this could be a wrongly shaped lever issue?

Could someone give me some advice on replacement levers? I kinda need one now. I loved the feeling of the short lever on my buddy's new KTM.
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