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Bleeding the front brake?


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Get a large syringe at a cooking store and put some aquarium hose on it. While your assistand pours in the new fluid, you are sucking it out through the bleeder valve on the caliper. Before you stop sucking it down, close the valve so that you will not end up releasing the preasure and allowing air to venture in through the threads of the nipple. It really is a simple process with 2 people. With one, it is a pain in the %$#.

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Hey Jeff. I just tried your method and when I was drawing fluid through the bleeder screw, it was sucking in air between the screw and the caliper body. So I tried it the other way, pushing fluid up through the bleeder screw into the reservoir. I'm not sure if I got all the air out...the wife was helping and she said she only saw a couple of bubbles...of course it didn't help that she was tipping the reservoir over letting the fluid spill into an empty oil can - instead of keeping the bottom of the reservoir covered with fluid. Maybe I need to do it again. The brakes don't feel as firm as before but I'll have to see if I can do 'stoppies' in the driveway.

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I totally know what you are talking about with the air being drawn it. The trick to it is not to open the valve alot. Apply the pull before you open up the valve and slowly turn until you start to draw the fluid out. I bleed my brakes every 2-3 races since I cook the fluid, so I have had many trial and error sessions with it. Try it again and see if it works any better.

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I just bled my front brake about a week ago. It took me 10 minutes following this simple process:

Before you start you will need a syringe. If you know a doctor or a medical supply store is nearby, get a 20cc syringe with a "Luer Lock" tip. This is most important! The Luer lock is threaded and big enough to hold regular fuel line - which fits perfectly on the bleeder screw (you can use this for bleeding the hydraulic clutch as well).

Follow these steps:

1) Remove top of master cylinder

2) Loosen bleeder valve on brake caliper (make sure you have some kind of can to catch the fluid).

3) Squeeze the brake lever to remove excess fluid

4) Using the syringe, suck up NEW brake fluid - do not try to recycle the old stuff!

5) Holding the syringe upside down, squeeze the fluid until all air bubbles are removed. If you've done heroin before, this should be easy 🙂

6) Press the end of the tube over the bleeder valve, which should still be loose. This can get messy, but if you hold the tip of the brake line firmly while you press it over the bleeder valve, it should slide right over it on account of the slippery brake fluid.

7) Compress the syringe, forcing the fluid up the brake line and into the master cylinder. Doing this ensures little to no air makes its way into the brake line.

8) Keep just a little bit of fluid in the syringe, but don't remove it from the screw just yet.

9) The objective here is to tighten the bleeder valve with the syringe still attached - so as to not allow air in.

10) Check the master cylinder to see how much fluid made its way to the top.

11) Refill the syringe, re-attach it to the bleeder valve, unscrew it and once again, force the fluid up to the master cylinder.

12) Repeat this process until the master cylinder is almost overflowing.

13) Once the master cylinder is completely full, loosen the bleeder valve without the syringe attached and allow enough fluid to escape so the master cylinder fluid level is just right (refer to manual for proper fluid level). You have to let a little out at a time obviously because you can't see the master cylinder and control the flow of fluid at the same time. I just let out a little bit, tighten the bleeder valve, checked the master cylinder and repeat until the level was just right.

14) Tighten the bleeder screw and put the master cylinder cover back on.

15) Compress the brake lever until pressure is back up.

As long as this process seems, it should only take 10-15 minutes once you master it.

Good luck.

-Justin

2002 KTM 520MXC

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Also try this little trick, once the bleeding job is done, get a zip tie and zip tie your brake lever into your throttle (firm but not too hard), turn your handle bars to the left so the master cylinder is at the highest point (you may need to tie the high point of the hose down lower than the master cylinder) and leave overnight. Any air in the system will slowly work it's way up the line and out of the master cylinder leaving you with a rock hard lever when you remove the zip tie.

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If there is air in the line it sometimes gets stuck in the loop and is hard to move up or down. This happens when the master cylinder gets too low. Fill the master cylinder and remove it from the bars. Hang it upright so the bubbles in the line will go to the top. Work the lever and air will escape. Tap the line to get it moving and work the lever some more. Reinstall and recheck the level.A little air makes a huge difference in feel.

If the air got into the caliper thru the bleeder from improper bleeding then redoo it with any of the above methods. Teflon tape on the bleeder threads helps the air leak problem. I use a mityvac to suck the fluid thru. It keeps a suction going as you refill the master cylinder and pump the lever. Good way to change the fluid.

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