Brake Bleeding

ok I am at a loss, neither front or rear can build pressure they just feel spoongy.

Lets start with front, have rebuild caliper, new line and new 11mm brembo MC. I used my vacuum pump to pull fluid through and kept getting air. Did some review on line and broke the fittings at MC and caliper to free any air. Also replaced bleed nipple in case.

Moved onto manual open/close of nipple while pumping with the lever. In between closing nipple and releasing lever I would pump it multiple times to build pressure. Still can not get lever to build pressure even after passing a bottle or so brake fluid through. What am I missing?

Try bleeding the M/C itself.
Unhook the line at the M/C. Place a finger over the hole in the M/C. Pump lever slowly. As you pull lever pressure will build up enough to squirt fluid out around your finger. Release lever your finger seals the M/C so it can pull more fluid out of reservoir. do this few times.
If you have an old brake line you can cut the banjo fitting off on end. Cut as close to the rubber as you can/ This leaves a short stub of tubing. Hook a hose, I like clear, to this stub. Hook this fitting on the M/C so the stub points up. Have the hose just long enough to go over into the reservoir. Then slowly pump lever. Repeat as need to see the hose full of fluid.
Once you have the M/C bled by either method quickly remove your finger or the banjo fitting and hose. Hook the brake line back up. I sat quickly because you don't want to let to much fluid get out of M/C.
Now once that fitting is tight, work down the line to the next fitting. Bleed at this point. Go to next fitting, bleed. Repeat till you get to caliper.
Another way to bleed the system is to remove the caliper, line and the junction block on the lower tree with out taking anything apart. Suspend the caliper above the bike so the line is as straight up as you can. Put a piece of wood or something between the caliper and piston or the brake pads so the piston won't come out.
Air float up, With the caliper and line above the M/C when bleeding helps the air do what it naturally does, Float up to the caliper. Once done put it back on the bike.
This last method was the only way I could get the rear to bleed. The way the rear M/C mounts and the line hookes to it it leaves a high spot in the line that make getting the line air free.
Leo

I am at complete loss, cut old hose and bleed MC by looping into reservoir. Then installed line and did same with line at caliper. I could feel more pressure at lever. Installed onto caliper and while holding caliper above bars bleed it. No pressure at lever again. I have the caliper suspended in air above MC overnight and will try bleeding again in morning. Not sure why this is being so difficult...

One more thing, when pulling lever i get piston to extend about 1/8-1/4" and pulls back in when releasing lever. No more no less and piston doesn't seem to extend any more than that. Issue and or contributing to problem?

I’ve had success in the past by simply placing a zip tie on the brake lever and leaving the system open overnight. This allows air in the system to rise to the top and evacuate through the mc.

WBacon said:

I’ve had success in the past by simply placing a zip tie on the brake lever and leaving the system open overnight. This allows air in the system to rise to the top and evacuate through the mc.

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Yeah, this works.

What a pain but I think I am there, out of the complete rebuild the “easiest” part has become the hardest. I did notice when applying front brake the banjo bolt on caliper has the slightest leak, using my finger ther is small amount fluid on it. New cooper and banjo bolts, keep tightening it down or wait for things to settle in?

Its should not leak could be some dirt from keeping it from sealing. It shouldnt be that much of a pain to bleed. I just got done doing my front brakes on my Roadstar and have simply cracked the banjos with leaver pressure cause sometime there could be trapped air. Only took me 30mins to bleed. But i also took the master cylinder cover off and zip tied the lever to the bar for 5 hrs and now its real good. Good luck

One item that I would strongly recommend is a speed bleeder.
http://www.speedbleeder.com

WBacon said:

I’ve had success in the past by simply placing a zip tie on the brake lever and leaving the system open overnight. This allows air in the system to rise to the top and evacuate through the mc.

Click to expand...

mrtwowheel said:

Yeah, this works.

Click to expand...

I read about this a gazillion times and I'll be damned if I can figure out what you guys are talking about. Not sayin' it doesn't work (never tried it), I just don't understand how it works. Trapped air escapes through the inlet port up into the reservoir. When you squeeze the lever, you block that port off. No place for air to go. What am I missing?

OK, so the port is closed, that doesn't stop the air/bubbles from coming/floating to the top, or, as high as the bubbles can go. That little bit of pressure must make it work better than the system just sitting idle because I don't get anywhere near the same results when I just let it sit without tying off the brake lever. Got spongy brakes? Tie it off and check in the morning, it always works. Yeah, I've bled them after doing this too. I've also bled them and then tied them off overnight.

Scott

Thinkin' on this, when the hydraulics are compressed, the bubbles are smaller, but their density is higher. Being smaller may prevent them from blocking and being trapped, but higher density will have them floating upward slower. It'd be fun to watch this on a clear tube. Any studies on this?

TwoManyXS1Bs said:

but higher density will have them floating upward slower.

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Right.... but they would still float upward, being lighter than the liquid they're floating in. Air gets trapped when it meets a pathway that goes downhill. Gravity takes it to the highest point and it can't make the journey downhill (even slightly) unless the fluid is helping it in that direction... bleeding for instance. I'll take everyone's word for it that it works, but I'll be damned if I understand how.....

The *trapping* I was thinking of is when the bubble is larger than the hose ID, and/or when multiple bubbles clump together. Like when you see an air pocket in the fuel line...

Oh man! I wuz avoiding taking the bait..
AFTER pulling fluid down through the bleeder with suction....
I'm in the closing the ports is counter productive camp. It's all about arranging a completely upwards path. With an angled reservoir special you may need to remove master from the handle bar to get that. (rear brakes need parts removed to get an all upward path also) Most bikes; on side stand, fork turned to left lock is enough. Usually 15 20 minutes does it. With the cap off and NOT upsetting the sidestand, bar left set up, I give the handle a few pump, release, waits, watching to see any last little air bubbles "stuck in the MC bore" escape, done. Between front brakes and hydraulic clutches I've done over 50 overhauls, always works.
Caveat; ALL rubber seals, slides in the caliper must be moving freely. A sticky piston seal or that rubber caliper mount sleeve on the later calipers will "spring" and return to it's original position each time you pump the lever during bleeding. Result? the piston never "pumps out" so the pad contacts the rotor and you merely tread water never getting a hard lever. It's a bit of a stretch but you can see this counter productive monkey motion if watch while working the lever. Remove caliper to make it easier to see whats going on. I have used the; extend caliper pistons as far as they will go, fill caliper with fluid, connect the line(s) then retract pistons with screw driver or other lever method, when fluid shows up in reservoir you have a bled system. but seriously it's not needed on the fairly simple XS650 set up.

gggGary said:

I have used the; extend caliper pistons as far as they will go, fill caliper with fluid, connect the line(s) then retract pistons with screw driver or other lever method, when fluid shows up in reservoir you have a bled system. but seriously it's not needed on the fairly simple XS650 set up.

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Yes ! Although I've only brake bled on the 77 and up XS model brakes, All the reported difficulties have intrigued me.
A good working Master Cylinder is vital.
If that is the case, dry lines seem easily bled even.
I use a "tapping on the open master cylinder"
to watch the bubbles float up method.
Just a little motion on the brake lever encourages the bubbles to rise right up.
Then, lever pumping the fluid through the system into a hose in a bottle attached to the bleeder valve While opening and closing the bleeder valve accordingly has worked easily on my own XS's.

Maybe I just get lucky but I don't encounter too many issues with brake bleeding either. I use a Mityvac vacuum pump (the deluxe all metal unit) to start, to fill the system, then finish with a few old fashioned hand pumps. I find this is required because you always see some bubbles with the vacuum pump, even after the system is full. I guess the pump is pulling so hard, it sucks some air in around the bleed nipple threads. This fools you into thinking there's still air in the system when that may not be true. The traditional hand pumping will show you there's not.

If I do encounter a stubborn one, I can usually "fix" it with a little "back bleeding", pumping fluid back into the system from the bottom up into the MC. My deluxe Mityvac is equipped for this. It has 2 ports, one creates a vacuum and pulls fluid, the other pumps pressure out and pushes it.

Proper tooling for jobs such as brake jobs for example does sometimes depend on the individual owners needs or the frequency of performing the tasks at hand.
Many members here work steadily and often on these XS's and fully benefit from a very well equipped shop.
Some members here are maintaining their one project and thus have different tooling needs and or budget. Because of these varying needs at times there is no hard line recomendation for which best tooling is needed.
All methods are the "best" in different circumstances as long as we can learn and accomplish our mechanical goals too.
-R

Whenever I have to open a brake system I start with a new brake bleed screw. Before bleeding I make sure that the bleed screw is sealed with Teflon tape or sealer that comes on the new screw. Teflon tape must be applied without covering the holes and so that no pieces of the tape enter the system.

Scott

OK, I'll admit I'm a tool guy, lol. I bought my Mityvac many, many years ago from, of all places, JC Whitney. Even back then it was expensive (about $50) because it was the deluxe model, but man oh man, have I used this thing over the years. Actually, I originally bought it to test for vacuum leaks on one of my cars, not for brake bleeding, but it's my main brake bleeding tool now.