problems bleeding front break


10 replies to this topic
  • lee-yzf426

Posted August 07, 2010 - 10:40 AM

#1

i cant get my front break to bleed at all ive tried and tried,

first off the seal in the master clinder is huge when pushing in it jst scrunches up in the middle, should it be that big.?

i fill the m/c to maximun mark then put the cap back on i can then feel a tiny amount of pressure, then wen i try bleeding it dissappears, it smeam's as if its drawing in air from somewhere , ive tried using the vacume thing aswell but still nothing, i think thats theres air coming in from somewhere because when using the vacume it just keeps bringing through air constanly way more than normal, i cant notice any leaks or anything, where should i be checking or am i doing something wrong.

any adive will be great

  • Timm

Posted August 08, 2010 - 06:41 AM

#2

here is what i do.took one of my wifes large seringes(for her horses.I don't think she uses it on herself)Attached a small hose on it.you need the same diameter as the bleed screw.Draw in the fluid,put it on the bleed screw,loosen the screw,push in the plunger,tighten the screw before removing the pressure.You might want to loosen the cap also.works for me

  • mike_dean

Posted August 08, 2010 - 02:54 PM

#3

I've had trouble also, especially with the stock brake hose that loops under the fork, the syringe method works the best, take the cover off the master cylinder and force the fluid up from the bottom, then when you are done pull the lever in part way and tie strap it to the bars and let it sit overnight so the air can rise to the top and it should be OK.

  • BlindLOKI

Posted August 08, 2010 - 09:51 PM

#4

make sure your pistons arent sucked all the way in as well... if they are too far in they will actually block the passageways for the fluid to fill the caliper and push the pistons... just a thought

  • 09speeddemon

Posted August 08, 2010 - 10:02 PM

#5

I had this same problem on my 03 450 and it was the master cyl i rebuilt it and that took care of the problem. How i found this out was i took the hose off on the master cyl on the bars and stuck my finger over the hole ( bench bleeding) and it would not build pressure.
Hope this helps

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted August 09, 2010 - 05:55 AM

#6

make sure your pistons arent sucked all the way in as well... if they are too far in they will actually block the passageways for the fluid to fill the caliper and push the pistons... just a thought

Not possible.

  • BlindLOKI

Posted August 09, 2010 - 06:25 AM

#7

Not possible.



maybe not on this model, but believe me it is... after you've seen something happen in person countless times it starts to become true :banana: In school when it came to bleed brakes I dont know how many people wasted a full 5 hour class bleeding brakes only to find out they didnt pop the pistons back out after servicing them... Just thought if he had possible worked on that end of things it may have something to do with it, sorry you disagree

  • grayracer513

Posted August 09, 2010 - 06:43 AM

#8

maybe not on this model, but believe me it is... after you've seen something happen in person countless times it starts to become true :banana: In school when it came to bleed brakes I dont know how many people wasted a full 5 hour class bleeding brakes only to find out they didnt pop the pistons back out after servicing them... Just thought if he had possible worked on that end of things it may have something to do with it, sorry you disagree

The caliper pistons of the Aisin units used on Yamahas will not occlude the feed ports when fully compressed. In over 35 years as a professional, I never encountered one on any vehicle that did.

  • BlindLOKI

Posted August 09, 2010 - 08:16 AM

#9

thats cool man, just letting you know what i've seen as well :eek: Not trying to start anything just trying to help, sorry bud :banana:

  • lee-yzf426

Posted August 09, 2010 - 10:53 AM

#10

been told that i could have a air lock any adive on how to remove this air lock from the hose

  • grayracer513

Posted August 09, 2010 - 11:48 AM

#11

You never said why you needed to bleed the brake in the first place, but boldly assuming without any reason to that your system is correctly assembled and in good health, the front brake should bleed by gravity.

The top seal is a bellows and should fold all the way back to a flat appearance. Open the reservoir and fill it leave the cover off. Open the bleeder screw and leave it open. Position the bars so that the bore of the master cylinder is horizontal to the ground. If fluid will run from the reservoir down and out the bleeder, just keep an eye on the fluid level and add more as needed to prevent it running out. When no more bubbles appear at the bleeder, close it.

If the fluid will not start down on its own, "tickle" the lever a little (moving the master cylinder plunger just a little, then letting it return) to get any air sitting in the fill port to burp up and out into the reservoir. Once the flow starts, let it go as above.

Once you've closed the bleeder, turn the bars slightly so that the hose end of the master cylinder is lower than the other, and move the lever slowly a short way, looking for any further air sitting in the bore to be forced up and out the fill port. If none is found, or once it seems gone, try the brake.





Related Content

Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Forums
Photo

Megabomb Fitment by 288yz450


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
Forums
Photo

James Stewart back on a YZ450F by YamaLink


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.