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  • Changing brake fluid

    What's the easiest way to change out the old brake fluid without introducing any air into the system(s)?

  • #2
    As long as you close the bleeder valve before you release the brake lever you won't introduce air. Procedure:
    1) Fill fluid resevoir
    2) steady pressure on brake lever.
    3) open bleeder
    4) just before or when brake lever hits bottom close bleeder valve.
    5)keep repeating until flushed.

    I usually will flush a 2 - 3 reservoirs per caliper for complete flush.

    Hope this helps..

    Comment


    • #3
      Why mix old fluid with the new fluid? That makes no sense. You should be able to drain the old fluid & have the brakes bled in 20 minutes.

      Comment


      • #4
        I agree. I should have started with remove fluid form reservoir. I usually use paper towels. I wouldn't go further than that so as not to introduce air into lines.

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        • #5
          On my bike (purchased used with no history) I wanted to change all the fluids before riding and have read some horror stories about bleeding gone wrong. All I did was park bike near shelf higher than my apes, used 1 foot of clear hose from new bottle of brake fluid into front fluid reservoir while it was still full. Then used vacuum bleeder to pull the entire bottle into left caliper until fluid came out clear, repeated on the right front caliper but not quite as long as the reservoir already had clean fluid. For the rear I just sat a 4x4 on my floorboard to hold the brake fluid above the reservoir. Worked for me..... good luck

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          • #6
            I was trying to keep it simple but, your system is interesting. Did you use a manual vacuum pump ? Something like MityVac?

            Comment


            • daveto
              daveto commented
              Editing a comment
              Air powered vacuum pump with a 2litre tank. It’s how I have done cars for 20 years, only difference is the hose contraption. For cars I have an adaptor to keep the bottle upside down over most reservoirs. Just don’t run out of new fluid or you get to start over. I also use the same vacuum pump when I’m done to set the reservoir to the correct level cuz it’s usually overfull.

          • #7
            Originally posted by RAM View Post
            I was trying to keep it simple but, your system is interesting. Did you use a manual vacuum pump ? Something like MityVac?
            Just go to a feed and grain store and get a large hypodermic syringe. Attach a vinyl tube to the end and suck the fluid down through the bleeder valve.

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            • #8
              Cover you tank/etc with towels and have some soapy water ready to immediately flush any brake fluid off paint...
              1972? Honda SL70 (dead)
              1978? Yamaha YZ80 (sold)
              1982 Yamaha 400? street bike (sold)
              2002 RoadStar (sold after 90,000 miles)
              2007 Stratoliner

              Some pictures here: https://www.dropbox.com/sh/fd9w68l93ngp8hd/GW6rxSmfza

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              • #9
                You could use a bulb syringe to remove most of the old fluid from the reservoir. Put a box end wrench on the bleeder. Attach 1/4th inch clear tubing to end of bleeder. put other end of tubing in a jar, submerged in fluid and lower than bleeder. Open bleeder. Add fresh fluid to reservoir ,slowly pump brake lever. Watch fluid become clear as it moves in tube towards the jar. Add more fluid as needed. Close bleeder and follow Scraper's advice about keeping brake fluid off the paint ! Cheers.

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                • #10
                  I invested in a set of speed bleeders for my bike off eBay. Beat the hell out of constantly opening and closing the bleeder valves while purging the new fluid through the lines and calipers. Everything else is the same, like others mentioned. Get as much fluid out of the reservoir as you can and fill with new. I had a clear hose over the bleeder and into a can to catch the old fluid as it is pumped out by working the brake lever / pedal. Make sure you keep a close eye on the reservoir level to not run it dry and thus pump air into the system.

                  Short version of the auction description:
                  The Speed Bleeder is truly a one-person bleeder screw. Once installed, it becomes a permanent part of the brake system. When it is time to bleed your brakes, you loosen the Speed Bleeder ¼ to ½
                  turns and pump your brake pedal or brake lever. When the pedal or lever is depressed the pressure generated opens the check valve letting air and brake fluid out of the end of the Speed Bleeder. When you release the pedal or lever and it returns to the up position, the check valve closes and prevents any air from reentering the system through the Speed Bleeder. When bubble free fluid is evident you close the Speed Bleeder. In the closed position it works just like your stock bleeder screw and prevents any brake fluid from leaking out. That is all there is to bleeding your brakes. If at a later date you need to bleed your brakes, the patented thread sealing system makes it easy to open the bleeder screw to perform the bleeding operation. It is made of quality materials:
                  Color : The color of the Speed Bleeders will vary from a silver color, to a gold color, to a copper color. All Stainless Steel Speed Bleeders are silver in color. Two of the Speed Bleeders are for the front calipers and one is for the rear caliper. | eBay!

                  Comment


                  • #11
                    --

                    I do like MBK does and use Speed Bleeders. It makes it so simple. As to sucking all the old fluid out first, I don't do that as it can leave an air bubble mostly in the T for the front calipers and it can be a bugger to get it out. There isn't that much fluid in the lines anyway, so you will get the old fluid out with just a few fills in the master cylinder.

                    --

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                    • #12
                      Not to be flippant, but if someone is having trouble bleeding the brakes or flushing the fluid, then they're probably doing something wrong. I'm always surprised by all the posts of people who struggle because it's really pretty easy.


                      Before you begin, you'll need a two foot piece of clear vinyl tubing, just large enough diameter to slip TIGHTLY over the caliper bleeder nipple*, and a small clear bottle or jar of at least 12oz or more. Skinny and tall works better than short and wide. An old beer bottle works well.


                      Starting with the front brakes:
                      - Before you remove the reservoir cap, wipe it down and make sure it and the reservoir is clean of *all* dirt and grime that may fall into the fluid. DO NOT LET ANY DUST OR DIRT GET IN THE FLUID OR ON THE COVER!
                      - Wrap a shop towel around the reservoir, because the stuff is HIGHLY corrosive and if [when] you spill any brake fluid, it will strip paint and EAT through rubber etc. if you don't WIPE IT OFF QUICKLY AND THOROUGHLY!
                      - Remove the screws and leave the cap on for now.

                      - Start with the caliper furthest from the reservoir [the left / shifter side.]
                      - Slip one end of the tubing over the bleeder nipple. [The tube should have to stretch a little to fit over the nipple.]
                      - Next, take bottle [or jar] and fill it with at least 3 inches of fluid.
                      - Stick the other end of the tube in to the jar; BE CERTAIN THE END STAYS SUBMERGED UNDER THE FLUID!!!
                      [This will prevent air from getting sucked back into the system.]
                      - Now remove the reservoir cap and top off with fluid if necessary.

                      - Next, begin pumping the brake lever until firm and HOLD it with one hand.
                      - With then other hand, using an open end wrench [or spanner for you Brits], loosen the bleeder nipple until fluid comes out. [Get a friend if your arms aren't long enough]
                      Note: don't over loosen the bleeder; just enough so fluid flows freely.
                      - AS SOON AS THE FLUID STOPS, CLOSE OFF THE BLEEDER BY TIGHTENING THE NIPPLE.
                      - Pump the brake lever again until firm and repeat.

                      - BE SURE TO KEEP AN EYE ON THE FLUID LEVEL IN THE RESERVOIR AND TOP OFF AS NEEDED!
                      [If you let the reservoir empty out, you will introduce air in to the system and cause MAJOR headaches.


                      That's pretty much it! Repeat this process until you see clean new fluid in the tube then move to the other side and repeat. After that go back to the left side and repeat again. You may still see some dirty fluid or small bubbles, so just keep alternating side to side until you see clean fluid and NO BUBBLES on both sides. It may take several cycles, side to side, to remove all the old fluid and bubbles.

                      - Repeat the process on the rear brake.

                      Tips: Secure the bottle/jar so it doesn't tip over. Also, as long as you have fluid in the clear vinyl hose, WITH NO BUBBLES, it's OK if some fluid gets sucked back in the bleeder while you're tightening the nipple. If you have a cap or lid for the bottle/jar, save it and the old fluid for next time.

                      That's' it. It should be a straight forward job and take less than 45 mins. And that's if you're taking your time.

                      P.S. Sure the speed bleeders help; but they're not necessary.

                      *Sorry but I don't know the exact tube size, it's about the diameter of a pencil, but the stuff is cheap and readily available at most any hardware store so get a couple different sizes to be safe.
                      Last edited by Doc_V; 01-01-2019, 12:33 AM.

                      Comment


                      • #13
                        All this sounds so complicated. If you can just take your bike into outer space you won't have to worry about air getting in there. See,
                        isn't that simpler?



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                        • #14
                          $1.87 for 12' of clear hose is all it cost. People make it MUCH harder than it really is. 8mm box end wrench is the only tool needed.

                          Comment


                          • #15
                            The lever was super jerky and coarse when I got my bike. I got some new fluid and bled the old out and cleaned the piston in the master cylinder. It took hardly any time at all. Once you get the process, you will be able to bleed calipers like a champ. I remember over thinking the process so much.

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                            • #16
                              why are you changing it ?

                              Comment


                              • TimB
                                TimB commented
                                Editing a comment
                                Routine maintenance is always a good idea

                              • fastjohnny
                                fastjohnny commented
                                Editing a comment
                                It is the original brake fluid.....I should hav4e changed it years ago...

                            • #17
                              Brake fluid should be changed periodically because it absorbs moisture and becomes less effective over time. Simple explanation. Google it for more detailed info

                              Or, come to the mountains and ride your bike hard for awhile for a first hand experience on why replacing old brake fluid is a good idea. I’ve seen it happen more than once.

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