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GURU
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1,797 Posts
Discussion Starter · #1 ·
So I got my rear mastercylinder and stuff today, I put it on and start to bleed it. I do so until no air is popping through the hole but it still isnt getting any tighter. Am I doing something wrong?

Method:

Pump 7-10 times, hold down, crack the nut, let it go until nothing comes out, tighten nut, release lever and repeat.

Can I use a speed bleeder?
 

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the mad doctor
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3,399 Posts
did you bleed the master cylinder?

take the brake line off at the master, stick your finger over the hole, and pump the lever a few times until it sprays brake fluid all over you :D.

also, if you have a high spot in the system, air will usually get trapped there, and give you spongy feeling brakes.

other than that, you may just have a bunk master cylider. maybe you're getting blow-by at the piston seal when you start to get pressure against it.
 

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GURU
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1,797 Posts
Discussion Starter · #4 ·
I hope its not blown I just got it. I dont notice anything leaking or anything like that
 

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Eff Tee Pee
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29,640 Posts
a lot of my buddies always say 'my brakes wont bleed' so i go and do it . just takes patience

i usually have someone there to squeeze the lever while i work the nipples ( :D ) pump pump pump pump hold..loosen nip. tighten nip. repeat other side. etc etc etc.

fun fun.
 

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the mad doctor
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3,399 Posts
Dudad said:
I hope its not blown I just got it. I dont notice anything leaking or anything like that

a blown piston seal wouldn't neccesarily leak, it may even bleed fine as it may not get any blow by until you get some pressure on it.

i'd try bleeding the master cylinder, then working your way down the brake system. trying to bleed an entire system with a dry master cylinder is a nightmare. usually ends up taking 4 times as long as it should, the air never really seems to want to come out of the master cylinder when you start with it dry.
 

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GURU
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1,797 Posts
Discussion Starter · #7 ·
I can see the brake pad barely move but I cant get it to move more than like 1-2mm. This sucks, Im about to say fuggit and run only front brakes who needs a rear anyway :moped_mazeguy:

How do you bleed only the mastercylindeR?
 

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GURU
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1,797 Posts
Discussion Starter · #8 ·
ok so I put my finger over the hole and kept pumping, nothing happened.......so then I pushed down without my finger over it, covered the hole, released, removed my finger, pushed, replaced let go........it eventually shot fluid out.........but if you left it uncovered for a few seconds you could here the pressure release.....is it supposed to do that?
 

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Eff Tee Pee
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29,640 Posts
im just picturing you at your computer desk typing away with brake fluid all over your hands. a bottle of dot 4 next to you and your bike leaking brake fluid all over your carpets...then your girl busts in catchin you red (hot) handed!

:LolLolLolLol:
 

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GURU
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1,797 Posts
Discussion Starter · #10 ·
bleh who cares, i keep washing my hands before i get on the computer. I give up for now, stupid rear brake
 

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the mad doctor
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3,399 Posts
um, it should have pretty much shot fluid past your finger after you pumped it a few times with your finger over the hole.

there's a tiny pinhole at the top of the bore that goes thru to the resevior (or the cap for the resevoir tube depending on what master cylinder you're using). make sure that isn't clogged.

if it's all clean, and you still can't get any pressure out of it, you can get a rebuild kit for any master cylinder for about $15

if you take off the master cylinder, and take off the rubber boot covering the pushrod, you can pop out the c-clip that holds the piston/seal/etc in there, just make sure it goes back in the same way it came out. while you have it apart, make sure there's no scores in the piston bore, that'll tear a piston seal reeeeal quick.
 

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the mad doctor
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3,399 Posts
929_adam said:
im just picturing you at your computer desk typing away with brake fluid all over your hands. a bottle of dot 4 next to you and your bike leaking brake fluid all over your carpets...then your girl busts in catchin you red (hot) handed!

:LolLolLolLol:
bahahahaha
 

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Wannabe
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1,502 Posts
Hmmm, well you have a couple of other options. You could just put the lid on and leave it overnight. The air will work its way to the high point. That may even things out, and make them a lot easier to bleed.

Stupid question time:
1) You have more fluid in the reservoir?
Hmmmm.... one sec.


Sevulturus said:
First thing I did was pop the seat and side panel off to give me easy access to the rear reservoir and sucked all the brake fluid out with a cheap syringe.



Then tape an empty bottle to the side of the swingarm, and stick an 8mm wrench over the bleed nipple, run a piece of hose from the bleed nipple to the bottle. Open the bleed nipple and pump all the brake fluid out of the line and the caliper body itself.





Disconnect your old line, but be sure to keep a rag around the bolt as it will still have some brake fluid in/on it. And that stuff will wreck havok on your tires or strip paint shortly after application. Close the bleed nipple



Pull out your old brake line, and thread in the new one.



Torque the sucker into place, and then get ready to bleed your lines.

The process is pretty simple
1) Fill the reservoir (keep an eye on this as the level will drop as the brake fluid moves into the line and caliper. If you let any air get in you'll need to start bleeding all over.
2) Pump the brake lever up and down several times, then press it down and keep it pressed down.
3) Open the bleed nipple on the caliper. Keep pressure on the brake lever.
4) You will see brake fluid mixed with air come out of the bleed line.
5) When the lever hits bottom close the nipple.
6) Repeat steps 1-5 until you no longer see air bubbles in the brake fluid. Make sure to keep the reservoir full.
7) Close up the system and use brake clean anywhere you spilled fluid (keep away from tires and paint).

Throughout the process be very careful to keep air from moving back into the system. Don't release the brake lever with the bleed nipple open, or allow the reservoir to empty.

I ran into a small problem, my rear line had a single rubber mount that could be slid anywhere along it's length. But it had to pass through two metal brackets. While it probably would have been okay to just leave it there and let it rub a little I didn't feel comfortable just leaving it like that. So I took the old brake lines and carved off a small section of the rubber surround.



Basically just a piece of rubber hose that has been slit down it's length. I just shoved it into the bracket and ziptied it in place.



This is stolen from my bike blog. It doesn't REALLY tell you how to install a master cylinder, but it walks you through bleeding the rear line, which is what you're having trouble with.

Are you totally sure that you've gotten everything torqued into place so it doesn't leak air?
 

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ADAM FAN CLUB PRESIDENT
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12,319 Posts
good write up man,how about some body puts something like this in the do it your self section
by the way im gunna give you some rep points for that :rock:
 

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The Soft Serve Enigma
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16,719 Posts
lol, Sev beat me! I read this and didn't have a chance to respond but I was gonna say, "ask Sev, he did this all yesterday and Monday!"
 

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GURU
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1,797 Posts
Discussion Starter · #17 ·
Well I woke up this morning and there was fluid on the rear wheel, so obviously there is a small leak somewhere in the rear caliper area.....i hate working on brakes.
 

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All star !!!
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6,714 Posts
Hell, am I the only one that does his brakes my himself and uses a vacuum bleeder?
 
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