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  1. #1

    Default 03 Sportster 1200 - Master Cylinder Issue/ Brake Bleed: NO FLUID

    i have looked everywhere and i cant seem to find an answer to this problem with bleeding my brakes.

    I have been in the process of rebuilding a 03 Sportster 1200 and I am currently reattaching the master cylinder and a new brake line to an aftermarket springer front end caliper.

    The master cylinder seems to be operating correctly. The plunger is pushing air through the system when it is depressed by the brake lever - i can feel it when i plug the m/c banjo bolt opening with my thumb (creates suction etc.) The issue is that even though it is pushing air, the fluid is not moving through the m/c. No matter how many times i pump the lever only air moves through, but no fluid. The fluid holes in the bottom of the m/c are free and clear of debris but still- fluid never comes out of the banjo bolt opening. I am totally stumped.

    Any ideas on what i am doing wrong here?

  2. #2
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    Bleeding these front brakes is a real pain, and unless you can pressure bleed it to get the process started, it can take a while.

    Specifically, your master cylinder has air in the cylinder, and fully bleeding it is a start. You need to have the master cylinder as level as possible, even if you have to remove it from the handlebar and attach it to something you can manipulate. Usually, turning the bars with the bike on the jiffy stand will allow you to get it level enough to bleed.

    Once the system is hooked up, I fill the master cylinder and leave the top off, and open the bleed screw on the caliper and let gravity take its course. A couple of reservoirs of fluid should be enough for this step.That will fill the caliper and get most of the air out of the master cylinder bore. Then, with the bleed screw closed, and the reservoir full, I pump the lever for a while, and air will come up through the relief port in the master cylinder. That does take a while. Then I bleed the brake in the usual way until I have a decent lever feel. This can all take a half hour or more, it's a slow process, and I don't know why it's so slow. Just takes patience.

    Jim

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    I've used a cheapo Mityvac bleeder for years. Makes quick work of the process regardless of your setup (I do not have the patience Jim is describing).

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    Quote Originally Posted by Vinson View Post
    I've used a cheapo Mityvac bleeder for years. Makes quick work of the process regardless of your setup (I do not have the patience Jim is describing).
    I've got a Mightyvac and I use it too. But on these front brakes, that alone doesn't do it for me, and so I end up going through the process above, after using the vacuum. It does help get things started though.
    (I found in using a Mightyvac on a car, that too much vacuum applied will pull air through the back plunger seal on the master cylinder, so some caution is needed.)

    Jim

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    Currently having the same issue with my rear m/c. Gonna have to look into the "Mightyvac"!

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    I've probably mentioned this before but one thing to be mindful of is the brake lever, especially if its an aftermarket one. I've seen some poorly made ones that wouldn't allow the m/c's piston to fully return 'home' when the lever was released and it made bleeding problematic.

    Also, vibrations can help free up air bubbles and allow fluid to travel down through the m/c and brake line. Just quickly tapping the brake lever less than 1/8th of the way through it's travel can accomplish this.
    Last edited by Skjoll; 10-15-2020 at 6:52 AM.

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    Quote Originally Posted by Skjoll View Post
    I've probably mentioned this before but one thing to be mindful of is the brake lever, especially if its an aftermarket one. I've seen some poorly made ones that wouldn't allow the m/c's piston to fully return 'home' when the lever was released and it made bleeding problematic.

    Also, vibrations can help free up air bubbles and allow fluid to travel down through the m/c and brake line. Just quickly tapping the brake lever less than 1/8th of the way through it's travel can accomplish this.
    I've come across the same thing with aftermarket master cylinders. Something to definitely be aware of.

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    I am having the same problem on my 2000 sportster 1200. Let me know what works for you and I'll try it.Click image for larger version. 

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  9. #9

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    Here's a few ways to do it.

    Keep a shop rag handy, whatever you choose to do below. And WEAR glasses. Ask me why..... And remember, the front MC, when the air is finally purged out of the system, will shoot brake fiuid under high pressure back out of it with zero warning: In your face and on anything nearby. Yes, brake fluid will stain and/or eat thru finished surfaces, (I have had Brake Fluid stain powder coat), if it gets there and you let it sit for more than a min or two. Have aniother cleaning rag and some sort of cleaner to remive the fluid (I just use windex or cut simple green) to clean off affected areas and used a good wax afterwards. ( Key is get the fluid off asap)

    1. On the caliper end, have a clear container on the ground that has fluid in it. Route a rubber line from the bleeder screw to the container, being sure the fluid level in the container is ALWAYS above the end of the rubber tube. (So air doesnt enter the tube)

    Position front end so brake MC is as level as possible: Remove MC cap. Open caliper bleeder screw about 1/2 - one full turn. GENTLY pump front brakes. Ensure MC fluid level never gets below level to allow air to enter line (Top off as needed). Also ensure the rubber tube end in the container doesnt suck air either. Pump brake gently. Gently tap the brake lines with a small wrench or screw driver from the calipers on up (Dont forget the line from the distro block up to the MC) If you get brake pressure, close bleeder screw, remove rubber hoses, Double check MC level Ive treid this technique a few times, not very very sucsessful at times. If it doesnt improve after 2 MC full of fluid, this technique isnt going to work

    2.This one has always worked for me 90% of the time:

    Place front end so the front MC is as level as possible. DO NOT open front brake bleeder(s) using the below procedure.

    With a shop rag handy, remove MC cover:
    While being careful NOT to spill or spray out fluid, gently pull tap the brake lines with a small wrench or screw driver from the calipers on up (Dont forget the line from the distro block up to the MC). Gently, but rapidly, pull/then release the front brake lever only about a 1/2 inch a few times. You should eventually see a small group of bubbles.. If not, tap the lines again and continue

    Be careful when you pull/release the brake lever: Once pressure builds you will start getting fluid feedback in the master cylinder and the fluid can shoot up in the air WITH NO WARNING. If after 15 minutes or so of trying and no improvement, move to the below technique

    3. This one ALWAYS works for me
    Keeping the front MC level as possible, with the MC cover still off, (all bleeder screws CLOSED) and the front brake caliper REMOVED, REAL gently slowly push back the disc brake pad inwards (the piston side) while a buddy watches the front master cylinder fluid. BE CAREFUL as fluid can shoot back out thru the MC. What you are really looking for is air coming back thru the MC. So be gentle and look for air. If you dont see air bubbles, top off fluid (if needed), put on MC cap, put brake caliper back on and pump the brakes a few times and you should be GTG . Repeat the whole procedure only once (two times total). If it doesnt work by now, this techniques will not work for you

    If the above doesnt work

    4. Take off MC cover: Open bleed screw and let gravity do the job for you. But you need to watch to ensure the MC fluid level does not allow for air to enter. Be patient, top off MC as needed as fluid drains out the bleeder end. DONT FORGET TO close bleeder once complete. Again, if 2 MC full of fluid passes thru and no joy, then your problem lies somewhere else

    Watch your brake pads and dont allow for fluid to contact them or the brake rotors. Use brake cleaner to clean them if it does

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    I have an early 70s front end on my bike and what I found to work was to remove the brake line at the MC until I see a little fluid work its way out. Then attach the brake line, slowly pull the brake handle, put your finger over the end of the hose and release until you get fluid. Reattach the brake line to the caliper and start using the bleed screw to open and close the line.

    The downside is you end up 'bleeding' the thing twice.

    I don't know why these units are so hard to get started but I feel for ya buddy

  11. #11

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    OP: Did you get it worked out? Beleive it or not, I just ran into the same issue, and none of my hints worked this time. Used my vacum bleeder and it took about 1 minute

  12. #12

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    I used a compressor operated vacum bleeder, about 80.00. I use it on my classic cars as well. The hand pump operated ones I quit using years ago. Ive had two go bad on me, but my compressor operated one works super great and fast

  13. #13

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    This is the one I use Very handy and fast. Be careful not to drain your master cylinder when using
    Attached Thumbnails Attached Thumbnails bleeder.jpg  

  14. #14

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    So whats the latest OP?

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