Front brake update, looking for advice
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  1. #1
    Member Dwight's Avatar
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    In a follow up to my earlier post on brake fluid and lithium grease: Well, after some effort, I was able to get one master cylinder cap screw out and drilled/easy-outed the other. I added some DOT 4 brake fluid and all seemed ok until I noticed a leak, I believe, at the juction of the feed line to the master cylinder, when I applied the brake. I think one of the washers plates at the junction is leaking. It leaks out to a certain level and then stops leaking. The brake works fine, but the fluid is below the level indicator. So I am trying to decide whether or not to replace the old unit with a new complete master cylinder, or just order a new diaphram gasket and two washer plates. How long do these units usually go before they fail? If I do go with a replacement, can anyone help explain how the front brake stop switch assy is disconnected? In any event, I will have to bleed the line. Would the best appoach be to disconnect the line at the caliper, drain the old brake fluid, reconnect, fill the reservoir, open the bleed skrew, pump the brake until fluid runs steady, close the bleed skrew, fill to level indicator and replace the diaphram and cap? Boat.net lists the washer plate as obsolete. Ron Ayers and Online Cycle Parts list the washer plate. On my Yanmar diesel engine, the fuel lines use copper washers at the connection points. Could I just buy some correct sized copper washers or does the DOT 4 fluid require special washers? I have come to use my rear brake more forcefully, even though the front still works, which is a good thing because I was favoring the front brake too much anyway. Thanks for any advice you can provide.

  2. #2
    Senior Member r80rt's Avatar
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    Did you try to tighten the bolt?
    Only a fool would attempt it, and God help me, I am that fool!

  3. #3
    Senior Member mtkd's Avatar
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    Mine has 7.5k miles on it and is from 2001. It was pretty gritty feeling and I thought I might have to replace it. I drained all the fluid and filled it back up with new fluid and it was a night and day difference. Not sure about leaking, but I would try and bleed them out and replace the fluid first.

    I didn't take the caliper off when I bled my brakes, I just opened the screw pumped it all out then filled it back up.

    Any chance of taking a picture of where it is leaking? For some reason I am having a hard time picturing it.
    -Szj



    2001 TW

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  5. #4
    Member Dwight's Avatar
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    I did try to tighten it, it was tight and didn't budge. Though I might try to loosen and then retighten, but it was getting dark and didn't want to mess it up. I'll try to get some pics tomorrow. I think the leak is up on the handlebar right where the line attaches to the master cylinder box. I would like to have washers handy if I loosen the connection so I can fix right away and not have the bike out of service while waiting for parts. When you say pump it out, do you mean just opening the bleed valve down by the caliper and using the hand brake to pump the fluid out?

  6. #5
    Senior Member r80rt's Avatar
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    I've seen banjo fittings leak like that after a good bump from falling over, you probably can loosten and clean it, then tighten it back up and stop the leak.
    Only a fool would attempt it, and God help me, I am that fool!

  7. #6
    Senior Member evan's Avatar
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    If its a banjo fitting and has sealing washers try what r80rt said and if still leaking replace sealing washers. probably any auto parts house will have them. just take them with you to match up. you should be flushing and bleeding out the brake fluid every few years because brake fluid does attract water and water in fluid not good. Flushing/bleeding the brake fluid system is always on my list of any quad or bike I get. It seems to be a easy thing to ignore/neglect for most owners. Maybe on motorcycles its different but when we flush car brake systems we never put brake pedal all the way to floor, only halfway. We have ruined a few old master cylinders putting pedal to floor and never fun to call customer to tell them they now need a new master cylinder.
    Mike Carter. Woodland, California (NorCal). '89 Tw200 (Black Widow Edition). Blood red Jimbo shield, Cycleracks, Nuvi 500 GPS, Kolpin fuel pack jr., D shield bark busters, 55t rear sprocket, Golden boy front tire, Ricochet shield.

  8. #7
    Senior Member Xracer's Avatar
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    I think you will find they are 10MM copper washers. Napa or Advanced will have them. Also I made a dandy brake bleeder from a turkey baster. What you will need. Baster,some 1/4" clear fuel line,Hose clamp for the fuel line and another to clamp the squeeze bulb to the baster. I've found bleeding the brakes from the caliper up to the master cylinder faster as it pumps out the air bubbles. Just loosen up the bleed screw, fill the baster with brake fluid,attach the hose to bleeder and squeeze. It help's to have someone watch the fluid level in the master cylinder as you don't want it to spill over. When no more bubbles appear tighten the bleed screw and check for a firm lever feel.Fill the master cylinder to correct level.Install diaphram and lid and your done.

  9. #8
    Member Dwight's Avatar
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    Thanks for the info guys. I took the cap off and drained the line at the bleed valve. The brake fluid was increadbly dirty and what came out of the line at the bleed valve was very watery and black color rather than clear. It clearly needed to be changed. There was some corrosion at the banjo junction, so I cleaned it up and reattached. The problem now is I may have messed up the master cylinder. I tried refilling the reservoir and pump it through the bleed valvle, but very little fluid will pump out when I apply the brake. When I put my thumb over the outlet of the master cylinder and apply the brake, I can feel a slight pressure and some fluid comes through but not very much. How much fluid should come through? Do master cylinders fail slowly or all at once? I'm going to try the turkey baster approach to inject new brake fluid, but wonder if I will need a new master cylinder anyway?

  10. #9
    Senior Member Xracer's Avatar
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    A mastercylinder as small as the Dub's does not move a lot of fluid. Also if there's air in the line you won't get much out.If there's no fluid leaks from the piston area I don't think you have messed anything up. Bleeding brakes from the top down is a royal pain in the arse as the master cylinder again does not move much fluid so the bottom to top method works much better with less risk of air bubbles being left in the system. Keep at it. You will get it fixed! Also how do your brake pads look? If there's plenty of meat left it's a good idea to take some fine sandpaper to them.

  11. #10
    Member Dwight's Avatar
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    Thanks Xracer, you were right on the money on all the issues I encountered. I replaced the the 10.3mm copper washers with ones purchased at the automotive store and constructed a turkey baster pump. To be honest, I didn't give it much hope, but it worked just as described. Two people does make it easier to see when the air bubbles end and the fluid level rises. Clearly, from the bottom up is the way to go. Given the poor quality of my old brake fluid, I would highly suggest checking and replacement if it looked as bad as mine did. Fluid should be completly clear. Other lessons learned: This Forum is priceless, don't be afraid to try fixes, listen to the experiences of those who have addressed the problems you have, go bottom up when replacing the brake fluid, and don't be afraid to ask when you need help. It is in the mid 70's here in FL so I get to go for a ride tomorrow thanks to Xracer.

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