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I rebuilt the master cylinder on Old Slagheap, and put on new braided brake lines. Now I'm trying to bleed the brake system. I've loosened the nipple on the caliper a few turns, and attached a hose to the nipple, and submerged the other end of the hose in a bottle of brake fluid. I filled the master cylinder with brake fluid. I've been pumping the brake lever back and forth, but I'm not getting any fluid coming out of the hose.

I searched on this forum and found an old post that said to just take my time, and only pump the lever a few times every few hours. I've been doing that for days now, but still no fluid is coming out of the hose. Now what?
 

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Sometimes their tough. I've had good luck with removing the brake master cylinder assembly friom the bike and the brake line from the caliper and letting the brake line hang straight down until brake fluid starts to drain out from the line. Then I attach the brake line to the caliper. And then I put the brake master cylinder in my vice and let the brake caliper hang straight down. I loosen the nipple and wait till fluid starts to flow out from the caliper. Then tighten the nipple. Mount the whole assembly on the bike then do the normal brake bleed like you're doing. Gravity is your friend in this case. Let it do most of the work before you try to do the final bleed.

Craig
 

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they make vacume bleeders you hook to your compressor hose. they kick ass. sucks the fluid right out. but i would just squeeze and squeeze and squeeze. it takes a while when its dry. like a long time. keep at it. or the gravity bleed method craig describes.

jc
 

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Like Craig says - get it started with a vacuum pump. MitiVac makes a pretty cheap setup - I think you can get it through Sears. Once you get some fluid started through it and break the initial airlock it'll go a lot easier. Starting from dry is a bitch with any brake system. Sometimes it's worth it to take a piece of 7/8" pipe and mount the m/c to it like a handlebar. On older GSXR racebikes I used to bleed the entire system off the bike - often with two helpers to hold, twist, raise, lower etc to try to get all the air out.

Also sometimes (especially with the FZR400 racers for some reason) we'd zip tie the brake lever back toward the bar and let it sit that all the way to the track bouncing on the trailer. Made a pretty big difference.

Michael
 

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No Mityvac= stick the hose from the bleeder in your mouth and suck. If you're a little good you can do it without getting any(much) in your mouth.
 

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I should also mention that from dry it'll take a couple of days. The tiniest of the entrained air bubbles take a long time to coalesce together so you can bleed them out. Tapping on things helps sometimes, as does thinking about where an air bubble will sit (banjo fittings, T-blocks, etc) and working out how to get it out. It wants to go up - most bleeding tries to push it down - a bit of a connundrum. You can crack banjo fittings like a bleeder - works great especially at the master cylinder. It's also messy - you'll need lots of rags and be careful of any paintwork.

Michael
 

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You probably have lots of air in the caliper, so you should unbolt it from the fork leg and use a c-clamp to press the piston(s)completely into the bore(s). That way you have a much smaller volume to bleed. Pushing in the piston also helps dislodge any air bubbles.
Ken
 

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Yep, if you don't have a vacume pump then hook clear tubing up to the bleeder and suck on that baby. You'll see the fluid before you swallow it.
JohnnyB
 

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Steve;

Your doing everything I would do to correctly bleed the brake lines. If your not getting any brake fluid through your exit hose, then you either need to loosen up the exit valve more or check for something that's clogging your brake system. You should get brake fluid through the system.

I might add (when you do start getting fluid thru the exit hose). While the exit valve is closed, pump your brake a few times to build up pressure, then slowly crack your exit valve while holding pressure on the brake handle. When the fluid start flowing thru the exit hose - allow the brake handle to go the end-stop (usually the handle bar) with the brake handle at the bar, close the exit valve of the brake. Before releasing the brake handle, ensure there is still brake fluid in the reserve - refill the reserve to capacity and pump up the brake again and repeat the process again.

BTW - having your exit hose submerged in a container full of brake fluid is the correct way to bleed you brakes.

If your still not getting anything through the brake lines, remove them and see if you can pass air through the lines - if that's ok then look for a UFO (Unidentified Floating Object) in your Master Brake Reserve that may be blocking fluid to the lines. If that's ok then try running a small wire in/out of the exit valve of the brake caliper. Be-careful, brake fluid will mess up your paint job.

Hope this helps
 

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1. gunk can clog the galley for the bleeder. besure that that is clear.

2. buy a mitty vac. put a 8mm wrench on the bleeder, then put the vacuum hose from the mitty vac on the bleeder. pump up the vac to 30 or 40 inches of hg.

3. Fill the master with fresh fluid as high as you can, put the cap on.

4. pump the brake 3 times and hold it in, crack the bleeder open 1/4 of a turn and let the vacuum suck on it for 3 seconds. close the bleeder.

5. make sure you still have vaccum pressure on the mitty vac.

6. repeat step 4 and 5 5 times while checking the master for enough fluid in between each time.

but make sure the bleeder isn't gunked up or you aren't going to get anything to come out.
 

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I just had a brake bleed issue with a sport bike this week. We tried to get the air out of the lines (back brake) and it just wouldn't clear it out. I remembered an old brake bleed trick and tried it with great results. The trick I used - with a bleeder bottle hooked to the brake port, I left the bleeder valve open and when to lunch. Gravity forced all the air out after about 1 hour. (the bleeder bottle must have fluid in the bottle for this to work) After lunch, I closed the valve, pumped the brake up again and gave it a few quick bleed shots, and the brakes were fine.

As a side note: Advance Auto Parts store I do business with will lend you tools for free. You leave a deposit, use the tool and you get all your money back when the tool is returned. This is a chain store and they may have this lend a tool program at your location. Check it out.
 
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