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Can not seem to bleed front brakes 1975 xs650
- Thread starter JNizza92
- Start date
whats the best replacement MC ? Someone recommended going with a smaller dia cylinder presumably to increase the pressure
I'm firmly in the smaller MC bore camp I have a 10mm bore (hard to find) and love it. I think anything smaller than the 14mm stock will an improvement. SS line should go with a smaller bore MC. Yes, smaller bore = more pressure = less lever pressure needed to stop. This increases "feel and your ability to modulate the stopping"
Since we are on the riff, the front brake is a critical component, new or rebuilt parts including brake lines are a VERY good idea.
Since we are on the riff, the front brake is a critical component, new or rebuilt parts including brake lines are a VERY good idea.
JNizza92
XS650 Enthusiast
I hooked up the mityvac today and it bled the rear just fine with no issues.
When I started on the front I ran into a problem.
I would pump up the tool to get a vacuum (20-25psi) and then crack the bleeder, but not a lot of fluid or air was getting sucked through, the vacuum pressure was not dropping either, it seemed like there is a blockage somewhere in the system...
When I started on the front I ran into a problem.
I would pump up the tool to get a vacuum (20-25psi) and then crack the bleeder, but not a lot of fluid or air was getting sucked through, the vacuum pressure was not dropping either, it seemed like there is a blockage somewhere in the system...
Are you still using the brake lines that came on the bike? If so that's the problem. The rubber lines rot from the inside out. Bits of the rubber hose break loose and can plug the line.
You bled the rear lines ok? The 75 didn't come with a rear disc brake. They can be added, I did on my 75.
Maybe you could list your bikes mods in your signature. I have most of the mods on my 5 listed in mine.
Leo
You bled the rear lines ok? The 75 didn't come with a rear disc brake. They can be added, I did on my 75.
Maybe you could list your bikes mods in your signature. I have most of the mods on my 5 listed in mine.
Leo
essexboydave
XS650 Enthusiast
Funny you should say that as although my brakes are now bled perfectly and they certainly feel right I just took it for a test ride and the stopping power is pretty scarey 
Next step is to fit a braided hose and new pads!
Next step is to fit a braided hose and new pads!
JNizza92
XS650 Enthusiast
yes, I did a rear disk conversion with the rear setup from a 78 special, I now have the mag wheels front and rear, I also have braided SS hoses front and rear. The front is one single line, none of that funky brake light switch stuff.
The front master cylinder I am running is the one from mikes, and the caliper is stock.
http://www.mikesxs.net/product/08-0255.html
The front master cylinder I am running is the one from mikes, and the caliper is stock.
http://www.mikesxs.net/product/08-0255.html
Paulrxs650
XS650 Enthusiast
I just fitted completely dry mc/. new braided hoses and refurb'd dry caliper and did my usual trick with some clear tube:
Fit everthing as normal. Fill the m/c with brake fluid. Attach a clear hose to the bleed nipple. Pull the lever in and suck, keeping a constant vaccum. Once the fluid starts to flow, stop (obviously dont suck too hard) then pump it through as normal. Works every time
Fit everthing as normal. Fill the m/c with brake fluid. Attach a clear hose to the bleed nipple. Pull the lever in and suck, keeping a constant vaccum. Once the fluid starts to flow, stop (obviously dont suck too hard) then pump it through as normal. Works every time
JNizza92
XS650 Enthusiast
I think my caliper is stuck then. I tried to bleed it conventionally for 3hours (pull level, open bleeder, shut bleeder, pump lever, then over again)
1974jh5
Curmudgeon.
The hoses that were on my bike looked fine but turned out to be so spongy I couldn't get a 11mm master cylinder to work. It took a braided stainless line to fix that.
JNizza92
XS650 Enthusiast
one of my buddies came over this weekend and we got it to bleed.
first we disconnected the line from the caliper, then I put my finger tightly over the end of the hose while he pumped the lever. He then kept the lever pulled in and I let my finger off and a little bit of fluid came out, but mostly air. We did it again, and again, and again until he started to get some feel to the lever, then he pulled it as far in as it could go and I let my finger off and we got a stream of brake fluid. We did this twice more then connected it to the caliper and bled it traditionally through the bleeder screw and it works great!
Thanks for the input everyone, now onto my clutch problem...
first we disconnected the line from the caliper, then I put my finger tightly over the end of the hose while he pumped the lever. He then kept the lever pulled in and I let my finger off and a little bit of fluid came out, but mostly air. We did it again, and again, and again until he started to get some feel to the lever, then he pulled it as far in as it could go and I let my finger off and we got a stream of brake fluid. We did this twice more then connected it to the caliper and bled it traditionally through the bleeder screw and it works great!
Thanks for the input everyone, now onto my clutch problem...
Curtis P
XS650 Addict
I bleed brakes differently from everyone else..
I fill the master up and crack the bleed screw open for a while, let gravity do its thing, once there is a trickle running out the bleed screw, I shut it then proceed with the pump up hold and crack bleeder business...
I fill the master up and crack the bleed screw open for a while, let gravity do its thing, once there is a trickle running out the bleed screw, I shut it then proceed with the pump up hold and crack bleeder business...
Paulrxs650
XS650 Enthusiast
Glad you got sorted!
glennpm
Another Old Biker Nut!
Good that you got it bled but it seems to me that it was much too hard to get fluid in the line. As Gary mentioned regarding the MC, "Is that tiny hole open? It is very small by design but does have to be open. There have been a few guys who bought a mikes MC and that hole was not open". It seems like yours could be partially obstructed.
I would also take a careful look at what DaddyG mentioned. "I bought three (MCs) from Mikes and all did the same thing would not bleed. So after i bought one from someone else i took one apart and found that it would only bleed if i took the lever off and bleed it that way. Looks like the plunger stays open with the lever on and sucks air. After i bleed it that way it worked and i took a little off the lever so it didn't hold the plunger open."
The tech link by littlebill31 http://www.xs650.com/forum/showthread.php?t=11205&highlight=bleed
You want to make sure that when you're on the road, that your brake is really working!
I would also take a careful look at what DaddyG mentioned. "I bought three (MCs) from Mikes and all did the same thing would not bleed. So after i bought one from someone else i took one apart and found that it would only bleed if i took the lever off and bleed it that way. Looks like the plunger stays open with the lever on and sucks air. After i bleed it that way it worked and i took a little off the lever so it didn't hold the plunger open."
The tech link by littlebill31 http://www.xs650.com/forum/showthread.php?t=11205&highlight=bleed
You want to make sure that when you're on the road, that your brake is really working!
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I realize this is an old thread, but I thought I would throw in my 2 cents. There are times when you can do everything right, or by the book and still not get any pressure on your brake lever. Especially when everything is new or rebuilt, and full of air. When bleeding by the book doesn't work, next I will "back bleed" from the bottom up with an oil can which I normally have good success with. If that doesn't work, then what I'll do is take off the master cylinder, brake line, and caliper all still connected and bring them over to my work bench. I put the caliper in a vise on top of the bench, and put the m/c on the floor, clamped so the top is level and it doesn't move around. (I use this method because I don't have any specific brake bleeding tools or a giant syringe.) The only other thing you need is a piece of clear tubing with 1/4 inch inner diameter. Only a couple of bucks from your local hardware store. I use one about 6 feet long to go from the bleeder valve down to the floor and back up because I don't want to get any in my mouth. Take the cap off the m/c in case you need to add any fluid. I'll usually suck on the hose to build up vacuum before I open the bleeder. Open the bleeder, suck a little bit and you will see a little fluid and air bubbles. Shut the bleeder while still sucking. A couple of times usually is all it takes to build up pressure on your lever if you have fluid in everything. It takes a couple of extra minutes, but this is my guaranteed method when all else fails, and the only mess you have to clean up is inside the clear tube.
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the mistake that I think a lot of owners make, is assembling the master cylinder dry . The piston and seals and MC bore should be liberally covered in brake fluid before assembly, or the piston has a tendency to stick at the end of the bore after the first lever pull and not return promptly
