Rear brake not working

[m2pete]

​

Thanks again Pieters86. My 3/8 was six-point. I bought a 12-point, and it works.

When I remove the brake line from the master cylinder and press the brake pedal, fluid comes out of the top, so I am thinking the master is ok. The fluid is clear. The only possible restriction seems to be the connection for the brake light switch (see attached). Anybody heard of fluid being stopped by this switch?

 

[Cooter]

Yes.

clear the line and banjo switch,

 

[m2pete]

Well, good news: I rebuilt the master cylinder with new parts, put everything back together, and filled the reservoir. Tried the old school method of bleeding the brake line by pumping the pedal and holding it down, opening the bleeder, closing the bleeder, then repeat. No fluid ever comes out of the bleeder and the pedal never gets hard, I think because the size of the master cylinder is very small compared to quantity of air that could be in the line? Is there a better technique, or do I need to purchase a pressure bleeder?

 

[Cooter]

the parts are still full of corrosion.

clear the line and banjo switch,

.

 

[Bueller-Bueller?]

I think your line is clogged. I would just replace it (amazon has lots of brake lines very reasonable) very least take it off and blow air it it. If the line is clear make sure the caliper moves.

 

[34nineteen]

Is fluid being pumped out of the master? Don’t worry about the bleed nipple at this point. You may need to “bench bleed” or “prime” the master first.

If a line was clogged, he would have a firm pedal.

If the master is not moving fluid, it doesnt matter what the rest of the system is doing.

The master is small enough where it’s not going to take a big air bubble to have the master (Baretts college nickname) “dry pump” (Cooters college nickname).

Start there.

Let me say it again.

Start there.

 

[Cooter]

Question for the OP.

When you "re-built the master", that included taking off the 90* plastic fitting that connects to the reservoir, Clearing that line, including the very tiny hole that feeds the master with fluid from the reservoir that is clogged with corrosion, and replacing that o-ring?

Your "rebuild" also included cleaning the fitting of the brake light pressure switch?

Disconnecting the brake line from the caliper and blowing compressed air through it?

We're trying to help you and now just guessing here, you're not doing such a great job of explaining what's happening.

 

[m2pete]

Yes, new 90 degree plastic elbow and o-ring, cleared the small hole, new piston and seals and spring. I think next step is try to force new fluid through the bleeder, after removing the line from top of master cylinder. If no flow, will remove brake light switch and one or more sections of line.

 

[Cooter]

 

[ajax5777]

I have rebuilt many a master cylinder but not one on my Buell, so I just want to through this out there cause its happened to me. And again, I have not rebuilt a Buell cylinder, but are you (OP) sure you put the part with the new cups in correctly? It will only work if the cupped rubber faces the correct direction. On some cylinders it is amazingly easy to put it in backwards, which would be much easier. Being from the school of hard knocks I've adopted a saying "if something goes together smooth and easy, you probably did it wrong". Just trying to cover everything. Good luck.

 

[m2pete]

Hello Ajax, thank you for your suggestion. I am sure the rubber cups were installed correctly, as it was clear how they went on originally, and clear how they are designed to scrape the cylinder walls. It is interesting to me that by pumping the pedal, I cannot build up any pressure, no matter how much air might be in the line. The master cylinder should be working like a one-way valve.

I am currently trying to remove the copper brake line between the reservoir and the brake light switch. Does anyone know what size socket is needed to remove the brake light switch? I tried an open-end wrench, but it is just too tight for that. The size is larger than 22mm, and less than one-inch, so that makes it 23, 24 or 25mm.

 

[Cooter]

No need for specialty tools, a decent sized syringe can be used to push fluid into the bleeder for 'reverse bleeding'.

Or something else to watch out for, if your still-filthy-not-cleaned rear brake caliper piston is sticky, it will retract back into its bore when you release the pedal, instead of staying out and causing the vacuum that's needed to draw fluid into the master cylinder bore. If that indeed is the case, you can see it happening.

 

[ajax5777]

It might be time to purchase a vac bleed kit, or rent one from a local auto parts store. It is a good way to at least get fluid in the line from the reservoir to the caliper. Once you get fluid to the caliper try finishing the job the old fashioned way to get solid fluid flowing. I had my ex well trained in the pump-hold-release method, current girlfriend is 'in training'.) I have also had some luck "snapping" the brake pedal/lever to get fluid to fill the master, snap the pedal a few times and look for air bubble(s) raising in the res. Brake bleeding can be a royal pain sometimes.

 

[m2pete]

Well folks, here is the latest: I purchased a syringe-type brake bleeder kit. Using either pressure or vacuum, I cannot move any fluid through the bleed nipple. The rebuilt master cylinder seems to be working fine, because I can build up pressure at the top when I remove the brake line. Tried to remove the brake light switch, but it is just too tight, so will have to remove the entire brake line and use a vise. The attached photo shows there is no fitting on the other side of the brake switch nut, so I guess I have to purchase a whole new brake line?

 

[ajax5777]

Well, once brake line is removed it will be the tell tale on if you can blow air through the line. The rubber sections would be suspect as the material breaks down and could actually works as a check valve, of course the metal sections can also plug with corrosion. I'm a little confused about your statement "because I can build up pressure at the top when I remove the brake line"?? Seems that with the brake line removed you should be easily pushing fluid out of the master, and if this is the case but nothing is coming out at the caliper end with the line removed, it would definitely point to a blockage in the line somewhere. If it were me I would be looking at replacing the entire line AND a caliper rebuild, or at least a disassembly and good cleaning.

 

[m2pete]

Ok, I tried blowing through the brake line, but it seems plugged. Anyone know of a fitting to attach to one end so that I can use compressed air to attempt to clear the line? The photo shows what both ends look like.

If I have to replace the line, any suggestions? I see some used and "not used" lines on Ebay, but not enthusiastic for installing another 25 year old line.

 

[34nineteen]

I'm sure you can buy a fitting to attach to the brake switch side of the hose, if you want to try to blow out the hose.

If you need a new hose, your best bet is to contact a company such as Venhill and you can make a custom line to replace factory one. If you want to keep a rear brake switch, use one that has the banjo bolt built into it (like what the XB's and other bikes use).

 

[ajax5777]

I would "make" my own. Aftermarket companies like J&P Cycle or Dennis Kirk or even Lowbrow Customs have a huge variety of different length hoses and different styles, coated braid or stainless steel braid, all different styles of banjo fittings in black, chrome or stainless with all different kinds of angles, straight, 30, 45, and 90 degree. They also have the banjo bolt/brake light switch combo mention above by 34nineteen, I have used the banjo/brake switch on several chopper projects with zero problems. With which ever styles you decide to go with, pay attention to the different thread styles and nut size to make sure everything will play together nicely. Take your time, make measurements and decide which angle banjos will give you the cleanest look and go to town and have some fun with it. you got this.

 

[m2pete]

I think the wires that connect to the brake light switch are not long enough to attach to the brake light switch if it is moved to the top of the master cylinder.

 

[ajax5777]

Splice splice baby. 8)) Just splice in as much wire as needed for a clean install. If you have a harbor freight(HF) near you, or any auto/hardware store, just get a wire stripping/crimping tool ($10-15 HF), some butt splices (variety box $15 HF, which will also have the different end pieces needed for a clean job) if needed, a roll of 18 gauge wire, I like to get this at an auto store, doesn't even have to be the same color, and if you really want to get fancy get some heat shrink tubing (small variety size pack $5 HF). The way i like to do a splice is carefully knock the metal splice part out of the plastic butt splice then slide a piece of heat shrink on the wire first, complete the crimp then slide the heat shrink over the splice and heat it up, either with a heat gun ($10 HF) or CAREFULLY WITH A LIGHTER. Or skip the heat shrink and just crimp it as is with the plastic insulator intact. Take your time and you'll be fine. I'm assuming you are using the banjo bolt/brake light switch, this bolt/switch comes with about 4-6 inches of wire attached which may be enough so you won't have to splice in extra wire but you will want to use a blade or bullet splice so as you can "disconnect" the wires from the switch if you ever need to remove the banjo bolt. If you only need to use blade/bullet splice you can get just a pack of those at an auto parts store for usually less than $5. You can also use the heat shrink on this type of connection for moisture protection, if you want but not necessary, you will just have to cut the heat shrink off to disconnect the wires. Hope this helps