1997 KX250 brakes

Hi, i have a 97 kx 250 i picked up in january.  It was in rough shape.  To get it moto ready i put new bar mounts, bars, bushings, levers, cables, grips, got the forks and shocks rebuilt with springs for my weight, etc.  (Summary at the bottom if you want to avoid the text wall)

First test ride out the bike randomly took off and looped me out and put me on my ass fracturing my tailbone (possibly, didnt go to the doc but i healed up great and am fine), tweaking the subframe pretty good etc.  I got it pretty straight but picked up another off ebay anyways along with new plastics.  Gelled fuel in the carb had the float stick and bike take off randomly, I have ridden it since and its all good now.

Onto my questions.  The brakes up front are not strong enough, or rather, it takes too much squeezing force to get the bike stopping well.  I have beat up forearms and hands from overworking myself in my teens and 20s and also just getting into this moto thing.  I used to just ride trails and farm ground and only went on a track a couple times but couldnt really ride them so I have some bad habits im trying to relearn.

The rear brakes were stiff when i got it but pads were worn and after putting new pads and bleeding as much as i can there is a good inch plus of brake pedal movement before it starts to stop.  Thats not going to work as im coming from a yz450F with lots of engine braking and need the rears to work as good as possible for my own safety.  I cannot figure out how to get the air out, i have a rebuild kit for the master cylinder i intend to install then try to bleed all the air out.

 

The front brakes are a little better, still some air but takes a lot of force to get the lever against the grip and it will stop the bike.  It takes a bit too much squeezing force compared to my 04 yz though and that is making it hard to develop confidence to come into turns hot when my hands get tired i have a hard time squeezing hard enough to stop the bike.  The master has a rod coming out with a nut and fitting i lost for adjustment and tbh i dont like the adjuster.  I found a 2010 yz450 front master and lever on ebay for $50 and im wondering if it would just bolt up.  The banjo goes in the back and not the front but i dont know if that would be an issue.  It would greatly benefit me to have level interchangeability between bikes and I much prefer the adjustment on the yz lever.  Im fine with the stopping power on my yz atm.

Also I have another set of 06 SSS forks i had on my yz that the chrome plating had started to peel and I think i found a source for aftermarket chrome tubes, i just have to figure out how to remove the originals from the lugs without destroying the threads.  Im thinking remove set screw and drill clear through the threads in the chrome tube then use heat to remove so i dont damage the threads in the lug, but that is a future project and i plan on running stock forks atm even though they def dont work as good as my 04 yz (I swapped to 06 yz250f forks i had rebuilt and resprung).

 

TL;DR  I want to swap from a 1997 front master cylinder to a yz master similar to the one on my 04 yz450 for lever interchangeability and possibly better brakes.  I also have air trapped in both front and rear and cant seem to get it bled off

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Rickyisms
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Location
FL US
4/17/2024 10:12am

Go to CVS and buy a small syringe and hook it to some fuel line for reverse bleeding. Before you reverse bleed, make sure you bleed at the banjo bolts at each master cylinder. Same process as bleeding through a bleed screw, pump the pedal/lever up, hold the pressure, and crack the banjo. To reverse bleed, Fill your syringe up with brake fluid, attach to the bleeder, open and force fluid through. Suck excess out of the master cylinder and repeat until your brakes are working. 

1
4/17/2024 4:37pm Edited Date/Time 4/17/2024 5:05pm

Well the rear I managed to bleed all the air out until the only slop was from the pin and clevis.  The front I had no such luck.  Nothing but fluid coming out the bleeder and banjo bolt and reverse bleeding seemed to do nothing but make it softer.

 

the rear did lose a little prime in the hour or two I was messing with the front and I feel like I hear it sucking air maybe from the connector going to the reservoir.  But I have a rebuild kit and o ring for the connector.  The front I can only assume is wore out or has dried up seals and needs a rebuild or replaced.

I had also at one point taken the bleeder complete out and just cycled the lever rapidly which pushed a bunch of fluid out but made no difference in lever feel, maybe fluid stuck in caliper?

MxAddic
Posts
2953
Joined
11/24/2022
Location
NY US
4/17/2024 6:18pm

The lines are probably spanked. I have a '96 with a Braking 270 rotor/steel line and it's the best brakes I have ever owned.

4/18/2024 10:40am

The rear bled off a bit overnight so I went ahead and rebuilt the master, it was nasty.

 

The front I tried putting the master on the ground below the caliper and unbolting the lower caliper bolt to get the bleeder as on top as possible.  It's as good as I can get it I measure the rotor and it's smaller than my Yz so maybe that's where the braking power difference is.  I still plan on swapping masters eventually I don't like the adjustment and I'm missing all the pieces.

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