Bleeding front braken issue

[Lluber]

Installed a smaller front master cylinder, everything seems correct (cables connected tightly no fluid leaking from the connections. topped off the new MC with fluid with the bike level, closed the MC top. Attached the bleeder to the nipple and pumped the lever, air bubbles came out. Eventually the bubbles stopped but the brake doesn't seem to be working. I did notice that the rubber insert that goes into the MC (between the cover and the fluid reservoir is a little saggy maybe thats not creating a air tight seal in the MC. Other then that Im not sure what else I'm doing wrong. tips pointers advice!

Thanks

 

[Lluber]

* Title should say brake not Braken!

 

[SLYrider491]

I've got the same thing goin on hopefully someone chimes in .. Can u show some pics of m/c you using

 

[Lluber]

THIS ones off a 08/09 ninja 250r.. the looks are great.. I just need it to work now!

 

[pjmule]

When I bleed mine I put a hose over the bleeder and the other end in a bottle of brake fluid and then pump the lever.Works for me.

 

[Lluber]

I had a little more luck.. My dumbass had put the cover inside the MC on upside down.. so once I put that back in the correct direction I had more success. The front brake is still a little spongy but I think with one more attempt to bleed it I should be able to get the remaining air out. I also tried the "loosen nipple, pump lever, tighten nipple, loosen lever" repeat method. This seemed to keep air from falling back down into the line.

 

[Square Circle]

I had a little more luck.. My dumbass had put the cover inside the MC on upside down.. so once I put that back in the correct direction I had more success. The front brake is still a little spongy but I think with one more attempt to bleed it I should be able to get the remaining air out. I also tried the "loosen nipple, pump lever, tighten nipple, loosen lever" repeat method. This seemed to keep air from falling back down into the line.

I was having issues with this also.. as soon as i high sided the master cylinder, a big air pocket rolled out up into the resivour, and bang i had lever pull. So start by filling MC with the caliper nipple open with a hose on it to an empty bottle until fuid comes out. Close nipple. Have just enough fluid in bottle to cover end of hose.. (i use clear tubing==hence seeing bubbles). make sure the bike is on sidestand with MC side of handlebars in its highest position.. fill resivour to its fullest you can. with nipple closed on caliper then pump lever a few times then... while holding fully back, open bleed nipple for a 1/2 second to expell air bubbles. Then do this a few more times, while constantly making sure the fluid doesnt drop past the outlet in MC. make sure you close the nipple off right away .. you should have a good lever pull now . Just put the cover back on MC. wipe up the brake fluid on bike parts. leave bike in side stand position and let it sit awile.. lightly wrap on the sides of brake line with but end of screw driver to drive any left over micro bubbles that are clinging to walls of line...they will fo up into the top of MC.. Happy Braking!

 

[peanut]

Put some strong elastic bands around the brake lever to clamp it so that it is under pressure then loosen the cap and leave overnight The continual pressure should gradually expell any residual air in the system

Read that somewhere on the forum ....not sure if it works or not as I haven't tried it yet

 

[Lluber]

im getting closer.. I ditched the little connector that came with my brake bleeding kit, and slid the hose directly over the bleeding nipple. now it seems like the issue is my brake lever hits the grip before it can build up enough pressure. wanna try leaving the MC cover off overnight to see if there a a few small bubbles in the line causing the sponginess.

 

[5twins]

When I get a stubborn one, I do a little "back bleeding". I pivot the caliper off the disc (or remove it) and pry the pads back into it with a flat bar. This forces fluid and any air back up into the MC reservoir. Many times, air bubbles get trapped at the 90° junction where the line connects to the MC. It's easier to force them back up into the MC than trying to get them all the way down the line to the caliper.

 

[peanut]

because you have the bleed nipple open there is no resistance to the fluid so it won't build pressure and you'll feel nothing through the lever.

What you should do is to crack open the nipple then slowly pull the lever and shut the nipple closed before the lever hits the H/ bar . then the return spring in the MC cylinder should return the piston assembly allowing fresh fluid to enter the cylinder from the reservoir.It may take a few minutes for the piston to return if it has new rubber seals fitted.

If no fluid comes out of the nipple when you pull the lever then your piston is stuck at the end of its travel and not returning to replenish the master cylinder with fluid.

Great idea by 5twins to get the piston to return

 

[jd750ace]

Another thing that helps is to "burp" the banjo fittings. It's the hardest spot to drive air out of. You will need pressure on the lever, and just crack them open till they burp out. Especially a problem if you have a splitter manifold. Burp them, then do the tension on the lever overnight. Just leaving the m/c cover off won't help. It should be vented on top anyway. If they are not, pressure can build with heating of the fluid during braking, and the brakes won't fully release.

 

[3Deuces]

I wound up having to force fluid through the bleeder on the caliper back up to the M/C with a syringe to get mine bled fully. 99 YZ250 M/C with a stock 81 caliper.

 

[weekendrider]

Lluber like several other adjustments on these we all have our own way.
And you are learning yours, keep at it, you are doing OK.
The reverse bleeding seveal have mentioned is becoming popular because it eliminates the squeeze,open + close bleeder, squeeze, open/close.
Never done it myself but the next time.......it may be a better way.

 

[retiredgentleman]

Not long ago, I installed braided steel lines on front and back brakes. My simple method is to prefill the brake lines while they are on the bench. Also prefill the caliper if it was empty.

I form a "U" shape so that both ends are at the same level. I then use a syringe to completely fill the line. While holding both ends level, I install the lower banjo fitting, and then raise the brake line to attach the upper banjo fitting. Add fluid to M/C.

In this way the lines,and caliper are full of fluid, so there is almost no air to bleed. I do a small amount of squeeze lever and bleed at caliper, but that takes about 5 minutes or less.

If you start with the lines full of air, that's a lot of air to remove.

 

[650Skull]

When pulling the brake lever or pushing a brake pedal on a car for bleeding it should be done quickly and the releasing done slow. Reason is the quick pressure will push any bubble along the line.

 

[peanut]

there are as many different recommendations as there are bikes
Some swear you should start with the nipple furthest away from the MC some say the one nearest the MC . Some say fast some say slow pumping .If you only have one nipple you haven't a lot of choice

I guess its best to use the method that works best for you with the braking system you are bleeding.


if the MC isn't pumping fluid due to a sticking piston as in this case I guess you have to modify your proceedure ,use back pressure from the caliper or pressurize the system etc

 

[pamcopete]

I use a variation of 5twins method.
1. Remove the caliper.
2. Remove the pads.
3. Position the caliper with the piston pointing down.
4. Squeeze the piston into the caliper bore.
5. Gently operate the brake lever to push the piston back out.
6. Repeat until your arms fall off and there are no more air bubbles exiting the MC reservoir.

Some people think that if you operate the brake lever with the caliper off of the bike that the piston will immediately shoot out of the caliper bore, but that is not the case. If you are really brave, you can pump the brake lever twice!

 

[gggGary]

How small is the master cylinder bore? A small master cylinder may not work with the stock rubber brake lines. They have too much "balloon" and a small MC piston will let the lever bottom before the lines are done expanding. I am using a 10mm MC with a one piece stainless line and great brakes and feel with lots of room between the lever and the handle bar took about 5 minutes to bleed, and parked over night up hill to the reservoir for HARD lever.