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Discussion Starter #1
Hey all I have an XS1100 ive been building and a while back I took of the front wheel to swap the 40 y/o tire and when I threw it back on I suddenly had little to no pressure at the lever even though I changed nothing in the brake line or MC. I rebuilt the MC, replaced the MC with a better brand (old one was a chinese clone I think) and while It definitely got better it still wasnt close to what I had before. I tried regular bleeding, reverse bleeding and few other things and then noticed I had a leak in the piston seal. One rebuild later and Ive still got the same issue. Do you guys think it's just that I suck at bleeding and its just bubbles? Or is there something I'm missing? Thanks for the help ride safe.
 

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Hydraulic brakes can only have a few things wrong with them.

1) Piston jammed/stuck
2) Leak
3) Air trapped in the line or cylinder
4) Seal in a cylinder allowing pressure to pass by
5) Check valve stuck
 

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Does your replacement MC have the required piston size? Not sure what that is on an XS, but a smaller piston will feel different.

Aside from that brakes are pretty simple, like Dods said. Master cylinders can be a pain to bleed though, so a persistent air bubble isn't out of the question. Sometimes what helps me is clamping the brake lever down overnight - it seems to allow the air bubbles to work themselves upward and out of the master if things are just right.
 

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Swamp Rat Rider
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Does your replacement MC have the required piston size? Not sure what that is on an XS, but a smaller piston will feel different.

Aside from that brakes are pretty simple, like Dods said. Master cylinders can be a pain to bleed though, so a persistent air bubble isn't out of the question. Sometimes what helps me is clamping the brake lever down overnight - it seems to allow the air bubbles to work themselves upward and out of the master if things are just right.
The Overnight thing has worked for me a couple of times .. Just thought would mention it in the hopes that might do it ..
 

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The banjo bolt area, where the brake line attaches to the master cylinder, often is a trouble spot for trapped air. When bleeding, tilt the handlebars to make sure the banjo bolt is lower than the master cylinder to give the air a chance to rise up. If this is not possible by turning the handlebars, either the bars or the brake cylinder itself might have to be temporarily loosened and relocated to a better position.
 

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There are master cylinders made in Taiwan that work. And rebuild kits for the originals. Sometimes bleeding seems to take forever. You could easily have sticking pistons. They can get pretty cruddy and rusty. If you have rubber hoses, you can clamp one off so as to check the function of the other side. That could half the head scratching, if one side is working as normal, and the other side is being naughty. The brake kits are not expensive, just a couple of pieces, so maybe you should remove the pistons for a look, and clean the calipers. Might as well put in new pucks while you are at it. Some models of the XS have weird shaped pucks. ( Pads )
There is also a good XS11 site. I have a sweet running 79 Special, that has a few rough spots, and a mint 81 Standard. Also have an 83 XS400. Did a slide on it in the rain. Back tyre is older than I thought and has gone hard I assume. Ordering new tyre today.

Unkle Krusty
 

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Discussion Starter #7
Thanks for all the advice. Will do the over night tricks a couple times and if that fails I'll rebuild the second caliper as well just to see if that's the issue, should be done anyways. Got new pads to go on once I figure out the pressure issue.

Also the xs1100 site isn't taking new members or they're excluding me for some other reason as I've applied 3 times over almost a half a year. I still read from there tho.
 

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Yep, the clamp clutch lever down over night has help me too. Also, after several hours clamped, to strike the lines and banjo bolt area and master cylinder with the end of a screw driver helps to dislodge stubborn bubbles.
 

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Discussion Starter #9
Yep, the clamp clutch lever down over night has help me too. Also, after several hours clamped, to strike the lines and banjo bolt area and master cylinder with the end of a screw driver helps to dislodge stubborn bubbles.
Done this for a couple nights now and even rode the bike up and down the street doing 40-50mph stops. hasnt gotten much better if any at all. Couldn't lock the brake if I wanted to. Either it's a really persistent bubble or maybe the spooge hole is clogged even though I cleaned it recently. Ill clean it all out again and see if it helps. thanks for the advice guys.
 

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Hey all I have an XS1100 ive been building and a while back I took of the front wheel to swap the 40 y/o tire and when I threw it back on I suddenly had little to no pressure at the lever even though I changed nothing in the brake line or MC. I rebuilt the MC, replaced the MC with a better brand (old one was a chinese clone I think) and while It definitely got better it still wasnt close to what I had before. I tried regular bleeding, reverse bleeding and few other things and then noticed I had a leak in the piston seal. One rebuild later and Ive still got the same issue. Do you guys think it's just that I suck at bleeding and its just bubbles? Or is there something I'm missing? Thanks for the help ride safe.
Hate to hear that last trick didn't work. But looking back at your original post, something about that swap has introduce a problem. When you bled the lines, did you get good flow or was it sluggish? I'm thinking you dislodged a chuck of jelled brake fluid. Lines aren't that expensive so if it was me, I'd just put new lines on. This way if you still have the problem there are only two places left and my next target would be the calipers. I forgot to look. Did you rebuild them? If not that's where I'd go next. If there was any jell in there you may have got some in there now as well. I know you might not want to do it but I think you want your brakes back more. I hate problems like this but when it happens to me I just keep removing one possiblity at a time.
 

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Done this for a couple nights now and even rode the bike up and down the street doing 40-50mph stops. hasnt gotten much better if any at all. Couldn't lock the brake if I wanted to. Either it's a really persistent bubble or maybe the spooge hole is clogged even though I cleaned it recently. Ill clean it all out again and see if it helps. thanks for the advice guys.
At 50 mph these things will not easily lock the front brake, and not even the back brake unless you stand on it. My 79 XS11 has a soft feel, and more travel, to the front brake lever compared to my other bikes. It is easy for the pistons to get stuck, and that would give you a hard feel to the lever, and not much stopping power. The pistons need to come out IMO.
Pump them out with the lever. Block the line of the first one to come out. There are other ways but that is the most effective. Decent pistons, new seals and a good master cylinder, and you should be good to go for many years. Then something else will show up. My red light came on yesterday, then off, then on and off.

Unkle Krusty
 

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Discussion Starter #12
I know it shouldn't be a breeze to lock the brake but it shouldn't go to the bar without some serious braking power, like I said I felt the brakes when they were still decent and I felt like I could lock it up if I grabbed a fist full of brake and she stopped well. Right now I have a weak feeling lever that builds a small amount of pressure and can go all the way to the bars. I also did disassemble and reassemble one of the calipers totally and honestly it was pretty clean inside with only a little grime. The gell thing however might be something I didn't think about. I do feel like the lever takes a little too long to return to open, it also could be some garbage in the unopened left caliper. I'll pop that one off tonight and see if I can see anything inside and give it a good cleaning and probably a paint makeover as well.

Regardless of the issue she is due for some new lines as well, anyone know where I can get some cheap brake lines or know the lengths of the current hoses (3 hoses with 2 hole banjo splitter)? I see theres a few SS line kits for the XS1100 but they seem expensive for what they are and I bet I could get them cheaper if I had the dimensions and went to someone in town. Thanks everyone for the help, Been working on this thing for almost a year now and I'm so close to ironing out the kinks and putting her on the road this season. Here she is if you guys were interested. First build and first bike.

 

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Agreed they are quite strong brakes when working properly. You middle gear drive has a square cover. All mine are round. There are some pieces missing from the rear fender. It is a Standard with the bigger tank, if you did not know that already.
MikesXS.com has some pieces. I will be replacing all the ones on my 81 Standard.

Unkle Krusty
 
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