johnsnownw Posted July 9, 2010 Share Posted July 9, 2010 Well, my local shop will not replace the Master Cylinder, so I have to figure out how to do it. I bought a replacement one from MikesXS, newer design, along with a braided brake line. I will be putting it on, hopefully tomorrow as my bike is having some things checked out at the aforementioned shop. I was wondering if anyone had any advice. I have purchased a mityvac brake bleeding kit, which should help things along a bit. Was just wondering if anyone has any knowledge of what I'm about to do, beyond what I have read online? That is to say, anything XS400 specific I need to know of or be careful with. I know I should be doing all the work myself, but there are some tools I don't have. As for the Master Cylinder replacement, I wasn't fully confident in my abilities to work on a vital safety bit of the bike, but now I have no choice. This is the last step on the bike before I can post a picture of her! Link to comment Share on other sites More sharing options...
OllieB Posted July 9, 2010 Share Posted July 9, 2010 Other folks with much more "XS" specific knowledge will probably chime in. I have some brake experience on bikes, scooters and cars, though. If the master cylinder you have is correct for the XS400, it should not be difficult. Once you have it mounted and the hose connected at each end and the bleed valve closed, fill the reservoir. I would use the new synthetic fluid usually marked as replacement for DOT 3/4. Don't use silicone fluid. It is not compatible with regular brake fluid. Now you connect the bleeder to the bleed nipple. Be certain the hose stays connected to the nipple. Some bleeders aren't that good and the hose comes off easily. Open the bleed valve about 1/4 - 1/2 turn. I usually hold one hand on the bleed hose/valve and use the other hand to wrench the bleed valve open. Begin pumping the vacuum brake bleeder. While you do want to suck brake fluid and air down through the system, YOU DON'T WANT TO EMPTY THE RESERVOIR, sucking more air into the system. As the level of fluid goes down in the reservoir, refill. Helps to have someone else to keep an eye on the reservoir. Once you think you have filled the system with brake fluid and purged all the air, close the bleed valve and squeeze the brake lever to see how it feels. As you probably already know, the lever should depress slightly then become firm. If it goes all the way down and/or feels spongy, you may still have air in the system. Sometimes with these tiny master cylinders you have to sort of prime them by squeezing the lever (holding it down), then open the valve slightly to allow air/fluid out. Don't release lever until valve is closed. May have to do this a couple of times. These systems are so small and move such a little bit of fluid with each squeeze that it is sometimes difficult to get trapped air out of the system. I have needed to use both the vacuum bleeder and lever squeeze method at times. Just cleaned the reservoir and flushed my XS400 system a couple days ago. Hope this helps. Link to comment Share on other sites More sharing options...
duaneage Posted July 9, 2010 Share Posted July 9, 2010 Well, my local shop will not replace the Master Cylinder, so I have to figure out how to do it. I bought a replacement one from MikesXS, newer design, along with a braided brake line. I will be putting it on, hopefully tomorrow as my bike is having some things checked out at the aforementioned shop. I was wondering if anyone had any advice. I have purchased a mityvac brake bleeding kit, which should help things along a bit. Was just wondering if anyone has any knowledge of what I'm about to do, beyond what I have read online? That is to say, anything XS400 specific I need to know of or be careful with. I know I should be doing all the work myself, but there are some tools I don't have. As for the Master Cylinder replacement, I wasn't fully confident in my abilities to work on a vital safety bit of the bike, but now I have no choice. This is the last step on the bike before I can post a picture of her! Was there a reason they would not replace it for you? Brakes are a critical safety element and I would think a shop would care enough about their customers to make sure they had good brakes. It's not a technically challenging task for a decent shop, unless they never saw disk brakes before. A list of ten hydraulic brake tips (suitable for framing) 1. Flush out the caliper. I would remove it and clean it out with the piston removed. 2. If the brake bleeder is rusty replace it. They are cheap enough. 3. Buy a new can of brake fluid, DOT 4 ( or 5 if your new cylinder calls for it) and keep it capped until ready to deploy. Don't mix fluids so if you are changing from 3 to 4 or 5 then you must remove all the old fluid. 4. Use new copper washers. Torque them to book specs. Don't reuse any copper washers even if they are only torqued once. 5.Use Denatured alcohol to clean up with. Do not use isopropyl alcohol as it has water mixed in. 6. Put the new cylinder on and use a banjo bolt with several old washers to cork off the output. Without a line on, get the cylinder primed and pumped up. You should have a rock hard lever that doesn't move much if at all. 7. add the caliper and line to the system and start sending fluid through. Keep the reservoir full and pump slow. Watch out for fountain splash from the bypass hole in the master when you let the lever go so protect the paint and other things with rags. 8. If you have trouble getting the air out, loosen the banjo on the master cylinder a little and bleed it out there first. 9. Once you have it bled out and it feels good, do several test stops in a row from 30 mph to heat up the fluid and check for leaks. 10. You might want to do an overnight test. This consists of wrapping a bungee cord around the brake lever to hold it down tight overnight. It should be in the same position in the morning with no leaks or changes. Link to comment Share on other sites More sharing options...
johnsnownw Posted July 9, 2010 Author Share Posted July 9, 2010 Thank you both for the responses, the information you provided will definitely be of use to me. As for why, the bike shop closest to my house doesn't like to work on bikes pre-1990. For the Master Cylinder specifically they said that often there are issues when installing new systems, and they have a cap on how much they charge for labor. So, if they can only charge up to 2 hrs in labor, and it takes them 4hrs to do it, they lose money. That is almost verbatim what the guy told me. Link to comment Share on other sites More sharing options...
Moderator mervin Posted July 9, 2010 Moderator Share Posted July 9, 2010 They need to get some new staff if they cannot replace a front master cylinder in 2 hours, maybe if you are going to rebuild it and have a tea break for an hour in between it would take 2 1/2 hours, It would appear you have some idiots there as we do here, oh by yhte way i have started putting modern master cylinders from ebay on my classics now FZR XJR being favourite merv Link to comment Share on other sites More sharing options...
OllieB Posted July 9, 2010 Share Posted July 9, 2010 Well, I suppose they could get into trouble on an old system with sediment or something messing up the caliper but it seems like a pretty lame excuse to me. This is pretty standard stuff that even a shade tree mech like me can perform. Of course there was the time with the master cylinder on my '90 benz ......... LOL Link to comment Share on other sites More sharing options...
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