Brake bleeding 101 and 102 - ZX Forums
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post #1 of 2 (permalink) Old 08-14-2013, 09:51 AM Thread Starter
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From: O Phuckin Hio
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Brake bleeding 101 and 102

Brake/Clutch Bleeding 101

Use high quality DOT 4 brake fluid (or preferred type) from a sealed container. Remove the old fluid from the master cylinder reservoir. Use a cooking type squeeze bulb baster to remove the bulk of the fluid. Use a paper towel to remove any remaining fluid. Top off the empty reservoir. Top them off periodically during this procedure. Do not spill any fluid on your bike because it may damage the paint. The front brake reservoir tends to spit fluid out the top during this process so make sure you place a bunch of rags, old blankets, or towels over the fuel tank.

You can make a bleeder drain container fairly easily by taking a plastic container with a screw on lid. Put a hole in the container lid just large enough to get the hose through. Put a short section of hose on the bleed valve on the brake caliper. Put the drain container on the other end to catch the runoff. You'll need to move the hose and container around to each caliper as you work, or use more than one container.

Use a wrench to open the bleed valve while simultaneously squeezing the lever (or pedal). About 2/3 of a turn on the wrench will do it. Fluid should run out of the hose at this time. When you squeeze to within 3/4 of your full lever pull, use the wrench to close the bleeder valve. It is important that you close the valve before hitting full travel on the lever. Release the lever and repeat the process (squeeze lever, open valve, close valve, release lever) until the fluid runs with no bubbles and the lever is firm. You'll be amazed how firm you can get your system.
While this way will work and there is absolutely nothing wrong with it, it is a big misconception that you have to shut the bleeder valve between every pump/squeeze of the lever. People do this on their cars, too. Pump, Open/Close; Pump, Open/Close…. You really don't need to do this. As long as you've got fluid flowing through the bleeder tube, you can just keep pumping/squeezing the lever until fresh brake fluids runs through the system. The end result is a flushed and bled system. Just make sure the reservoir stays topped off. If you bleed it dry, you'll have to start all over again. This how pro motorcycle mechanics flush a hydraulic brake system.

Brake Bleeding 102

Put the vacuum bleeder aside and bleed the brakes the common way. Vacuum bleeders sometimes are more troublesome than efficient. Allow the master cylinder to purge the system for best results. This may be slow and painful, but this is how we do it.

To begin, you will flush the existing brake fluid from the reservoir. You'll pump it through the lines, to the bleeder valves. Flush thoroughly until you see fresh fluid exit each valve. Start with the closest bleeder valve when flushing and work away from the master cylinder to the next furthest valve. When flushing, pump the lever a few times and hold, crack the bleeder wide open and leave it open. Begin pumping until you see fresh fluid at the bleeder. When you see the fresh fluid, hold the lever in on the last pump, tighten the valve, pump the lever, and crack the valve for a quick bleed. Repeat for all bleeders. You may not need to bleed the system after the last valve is flushed.

If bleeding is necessary, bleed the system by starting with the furthest bleeder valve and work towards the master cylinder (just the opposite of flushing).

If you must bleed the master cylinder (rarely) do the following: adjust the master cylinder so it is as level as possible on the handlebar. Remove the reservoir cap assembly and top off fluid to proper level. Very, very, slowly pull the brake lever in while monitoring the intake/exhaust ports in the bottom of the reservoir. Return the lever slowly, too. Alternate lever pulls of about 1-2mm and full pulls. The short pulls seem to work the air up best. Look for air bubbles to rise from the ports. Repeat until no air is seen or lever feels normal.

If no air is seen, pull the lever in and let it return quickly by releasing it from your fingertips. It should quickly snap back under the plunger spring's pressure. Repeat this several times while watching for air bubbles. Switch between the two methods described above: slow short pull method and long quick release method. If no air is observed either way, the master cylinder is purged of air. If you observed air bubbles, even one, repeat methods until no air is observed. This may take several minutes, be patient.

Tip: Shake or gently tap brake hoses with a tool to send residual air up the lines to the master cylinder.

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post #2 of 2 (permalink) Old 08-11-2015, 03:22 AM
1lightweight's Avatar
Joined: Jan 2015
From: Texas

Posts: 42
Thanks for the write up. I had no problem with my rear. But my dual front is giving me hell. I'll try these tricks
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