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I'm think I'm going to go insane trying to bleed the brakes on my damn bike. I rebuilt the front brake caliper, and the master cylinder seems to be OK. For the life of me I can't get the damn thing to build any pressure. I thought I was on the right track for a while, but now when I pump the lever and crack the valve, no air is coming out, just fluid - and the resivore doesn't seem to be losing any fluid. I think I may have some air in the brake lines or in the caliper. Any tips would be greatly appreciated, I think I'm going to go insane :mad:
 

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I would go get one of those brake bleadr kits. I forget what it is called. I got one when I had to fix my brakes and it worked great. Hook the tube to the bleed screw, pump the handle, open it up and you should suck the majority of the air out. You also might have air stuck up by the master cylinder, try bleeding it there.

I think the thing is called a mightyvac.
 

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StrickSVS said:
I would go get one of those brake bleadr kits. I forget what it is called. I got one when I had to fix my brakes and it worked great. Hook the tube to the bleed screw, pump the handle, open it up and you should suck the majority of the air out. You also might have air stuck up by the master cylinder, try bleeding it there.

I think the thing is called a mightyvac.
Yp this is def the way to go itll make your brake bleeding a breeze.

and yes it is mightyvac
 

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You may have some air bubbles trapped in the banjo bolt. When you're pumping the brake handle whack the upper banjo bolt with a rubber hammer and then bleed the brakes. Repeat as required.

Oh, and one of those brake bleeding kits is quite handy. I got a neat/cheap one from my local auto parts store that I've been pretty happy with.
 

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l also agree that you probably have bubbles in the master cylinder/banjo bolt area. Bleed that area through the banjo, or install a new banjo with a bleeder built into it. That makes life LOTS easier!

A long time ago, I picked up a 60ml irrigation syringe at a medical supply store. I use it backwards from a regular bleeder: INJECT fluid UP from the bottom and backfill all the way to the reservoir. Then you'll be able to bleed normally. Works great!

Scott :D
 

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I'm tempted (next time) to try a reverse bleed when I do my brakes... Any cons other than maybe overflowing the master if your not careful?
 

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Discussion Starter #8
Thanks much for the replies and the advice. I'm thinking that I have successfully bleed the master cylinder - I borrowed a kit for use with a car and screwed some fitting into the cylinder, ran a hose from the fitting back into the resivore, and it seemed to pump fine. I guess I didn't consider there being any air bubbles in the banjo fitting or anything like that. Perhaps I should try to bleed piece by piece down the line - since it has ablut 3 fittings before it reaches the caliper. I wouldn't have thought that a banjo fitting would cause much of a problem, as there's not too much room for any air in it. I think I'll end up purchasing one of those vaccum powered bleeding kits in a couple weeks when I can afford it. Anyways, thanks much for the tips.
 

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So how often should the brakes be bled on a modern bike?

SB
 

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you can make that same kit using a mustard bottle and a tube... try it :D:D

can you tell me why the master cylinder I just put on doesn't work?? I am getting no break preasure... I have not bled the brakes yet but I should still have something??? :( :(
 

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A trick that helps to get air out of the master cylinder, or lines, is to pull the lever all the way to the grip, and quickly move it in and out but only an 1/8" or so. Kind of like oscilating/vibrating the lever against the grip quickly. You should see bubbles come up through the resovoir when you do this (if you have air).

Shane
 

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Another neat trick to get that last bit of air out of the lines is to take a bungy cord, and wrap around the grip and the lever, with the cover off of course and covered with a cloth, and leave it like that over night and the air will come out of the lines by itself.
 

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Discussion Starter #17
Well, picked myself up one of those MightyVac things and all I can say is SWEEEEEEEET. There was so much air in my brake lines I would have driven myself insane trying to bleed them out without the proper equipment. Too bad winter's around the corner - I really wanna gain some experience (I'm a newbie). I do have a question regarding the front brakes though. My bike's a 74 Yamaha, and I had the lines replaced because they were shot. I noticed that it doesn't grab much when initially pulled, but grips well on the second pull (after it builds pressure). Can anything be done to correct this, and allow maximum grip on first pull?
 

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Discussion Starter #18
Oh yeah, one more thing. The fluid resivore cap says it takes DOT4 fluid, but all I had was DOT3. Will this cause any harm to my brake system? Just curious.
 

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Discussion Starter #19
Once again espresso, thanks for the great advice. I'll give that a shot. Much definitely appreciated :D
 

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Lets see,...
DOT 3, 4 and 5.1 are all compatible with each other and the higher the DOT number the higher the boiling point (which is good).

Every time your brakes get really hot and then cool, condensation occurs and moisture is absorbed which lowers the boiling point and when the fluid boild your brakes start to fade or in extreme cases fail completely. That is why it is important to replace your brake fluid regularly.

DOT 5 is silicone based and is not hydroscopic, meaning it won't absorb water, it retains its high boiling point over time, unlike the others which gradually absorb water and that lowers their boiling points.

Superficially you'd think that DOT 5 is the way to go - it has a high boiling point and it doesn't absorb water so, it lasts longer. But, some people don't like the brake feel when using DOT 5 and it can't be mixed with any of the other fluids (at all).

So, I'd suggest sticking with DOT 4 or DOT 5.1 for best performance, but DOT 3 won't cause you any problems with most street riding.
 
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