Posted May 17, 20213 yr Hi there so my ongoing project with the XTR has one thing left the front brake. When I got the bike the brake would build up pressure and then overnight would lose it again. I cant see any liquid dripping out of the caliper so i assumed that was ok and bought a master cylinder kit. Now my boy who the bike is for gets impatient and says let me take the bike into work and I'll get it fixed in my lunches. fast forward a month or two and it comes back to me with no work done at all but in the kit for the master cylinder there is now a ball bearing which I dont remember taking out of anywhere, is the ball a one way valve that I've overlooked. Ive checked the service manual and theres no balls anywhere. Ok so Ive put the new master cylinder in and i can get most of the air out of the system, but then the brake fluid comes out of the reservoir instead of moving the caliper. Parts for this bike are hard to find (discontinued) so could i replace the whole lot with a generic kit? Any help gratefully appreciated.
May 17, 20213 yr I would,, thers some good master cylinders on ebay,,even repro  rd ,, or K/h ,,  will do,Â
May 17, 20213 yr Moderator Keep looking!Yamaha XT 125x Xt125r Genuine Master Cylinder Front New Ajp High Quality Oem (ebay.co.uk) E-Bay is your friend!
May 19, 20213 yr Author Thanks for the help guys, I have replaced the master cylinder so thats better. I think the caliper has a leak/crack because fluid isnt coming out the bleed nipple itself, but the thread of the nipple. I may have to replace the caliper. I have found one on ebay in italy but it looks worse than the one i have so probably not worth it. can I get a different caliper for this bike? maybe off a YBR or something, although its on the wrong side so i dont know. Once again, any help gratefully appreciated!
May 19, 20213 yr Moderator 3 hours ago, UglierBoss said: I think the caliper has a leak/crack because fluid isnt coming out the bleed nipple itself, but the thread of the nipple. Woah, woah, woah, woah..! Chances are that if you had a cracked calliper, you'd know about it! It sounds to me like your bleed nipple is blocked. It's fairly normal for air/fluid to come out of the threads... 1/ Don't crack it open quite as far, it's only supposed to be cracked enough to let air out then nipped up again quick. 2/ Buy a new bleed nipple (I'm pretty sure they all have the same threads on them...).  Out of curiosity, how are you bleeding the brakes? Are you: a/ Doing it the old fashioned way and using the lever? b/ Using a vacuum bleeder? c/ Using a pressure bleeder?
August 2, 20213 yr Author Super thanks for your help. I have replaced the bleed nipple, put new seals in the caliper, installed a new braided line and changed the master over as mentioned above. Passed its MOT the other day and running fine.
August 2, 20213 yr Moderator On 5/19/2021 at 6:43 PM, Snakebite68 said: Out of curiosity, how are you bleeding the brakes? Are you: a/ Doing it the old fashioned way and using the lever? b/ Using a vacuum bleeder? c/ Using a pressure bleeder? No worries. Which way were you doing it?
August 3, 20213 yr Moderator Aaah, ok, I was wondering because depending on which way you do it, that bubbling out of the threads can cause you problems. Â Using the leaver or a pressure bleeder isn't bothered by it, but if you use a vacuum bleeder, there's a chance you can actually suck in some air at the end (been there, bit of a bugger!). A bit of thread tape cuts down the problem to the minimum...
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