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Discussion Starter · #1 ·
I have put in a new MC Rebuild kit into my 1981 Deluxe.Also had to buy a new fluid cup. According to schematic of my handbook everything has been put together in the right order. After I hooked up the brake line and filled the cup with brake fluid, I started pumping.......no pressure!! I disconnected the brake line from MC and pumped again and there is nothing coming out!!! Is there a trick to airbleeding a "dry" brake line? Does the system need some brake fluid in the line in order to have the MC be able to pump(priming)? I have taking the piston and spring out several times and do not come up with a solution. Has this ever happened to anybody?
 

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happens whenever your change your brake fluid. You have to just bleed the brake line till all the air is out and then pressure will be restored. And no trick that I know of except to keep squeezing.
 

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I have put in a new MC Rebuild kit into my 1981 Deluxe.Also had to buy a new fluid cup. According to schematic of my handbook everything has been put together in the right order. After I hooked up the brake line and filled the cup with brake fluid, I started pumping.......no pressure!! I disconnected the brake line from MC and pumped again and there is nothing coming out!!! Is there a trick to airbleeding a "dry" brake line? Does the system need some brake fluid in the line in order to have the MC be able to pump(priming)? I have taking the piston and spring out several times and do not come up with a solution. Has this ever happened to anybody?
yes,some help here............

http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=9&t=315
 

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It happens to all of us the first and sometimes even the second time.



I will assume that you took the time to clear out that TINY return passage on the master cylinder?



If you don't have one a vacuum bleeder from Harbor Freight Tools is cheap and works fairly well, you're liternally sucking the fluid down instead of trying to pump it with the MC.



Alternately, and this is known to work, fill the reservoir full then strap the brake lever pulled all the way back with a bunch of rubber bands or what have you and leave it overnight. When you go back to normally bleeding it the next day it's far easier.
 

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It happens to all of us the first and sometimes even the second time.



I will assume that you took the time to clear out that TINY return passage on the master cylinder?



If you don't have one a vacuum bleeder from Harbor Freight Tools is cheap and works fairly well, you're liternally sucking the fluid down instead of trying to pump it with the MC.



Alternately, and this is known to work, fill the reservoir full then strap the brake lever pulled all the way back with a bunch of rubber bands or what have you and leave it overnight. When you go back to normally bleeding it the next day it's far easier.
 

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I thought I had put the kit in correctly too, wouldn't build pressure no matter what I did either.



Took it apart and installed the kit correctly and all was good. I wish I could remember exactly where I went wrong on the install (it looked just like it was supposed to) but it was many moons ago.



Double check it, and if it looks like it can install in another orientation...try that.
 

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Leaving the brake clamped on overnight by rubber bands is a good idea and often a great help. If nothing else the line pressure helps consilidate the trapped air, ie lots of smaller bubbles join to become fewer larger bubbles. In cases where it really is being a pain you might find that unhooking the caliper and lines and suspending the caliper above the master cylinder helps. Its a lot easier to pump air up through fluid than down as part of the reason its hard to bleed is as soon as you release the lever pressure trapped air wants to rise, so the air bubbles are constantly going back and forth, so to speak.If you do, make sure you place something between the pads that is at least as thick as the disc to stop the pistons closing. You can also find that if you tap the brake lines themselves you help speed the passage of air as they form a meniscus off the inside of the brake line wall, in exactly the same way that you can see between mercury and glass in a barometer
 

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Discussion Starter · #8 ·
Thanks guys, I will try to let it drain into the line as marshall3 recommends, if won't do, i will have to buy one of those air bleeders. I was just puzzled that I couldn't even get fluid pumped out of the MC with the brake line disconnected. Oh well, I will keep you updated. Thanks again
 

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Thanks guys, I will try to let it drain into the line as marshall3 recommends, if won't do, i will have to buy one of those air bleeders. I was just puzzled that I couldn't even get fluid pumped out of the MC with the brake line disconnected. Oh well, I will keep you updated. Thanks again
I would take the line off the Master cylinder and hold my finger over the hole in the master cylinder and pump the lever to make sure you have pressure right off the M/C. As I recall there is a small hole in the M/C that can get clogged with krud. A vacuum bleeder is a nice tool to have.

Cheers, 50gary
 

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Sometimes it takes 500 squeezes of the brake lever to get pressure. Holding your thumb over the output hole while squeezing the lever sometimes helps.
 

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Sometimes it takes 500 squeezes of the brake lever to get pressure. Holding your thumb over the output hole while squeezing the lever sometimes helps.


Large Syringe and some 1/4 inch tubing. Connect syringe and tubing to bleed nipple on caliper. Remove MC cap. inject fluid through the caliper and up the line into the MC.



The holding the handle thing really is only for a final solution to soft brakes, not a complete bleed IMO.
 

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Discussion Starter · #12 ·
Okay, I got pressure now!!!!!! I did buy one of those vac pumps from Harbor Freight. Were on sale for $24.99. After that things went uphill. It still took while to get the MC to jump start, But the pump is the way to go. Thanks for all that advice. I was about to go crazy!!! Took the MC apart and stared at piston probably about 5 times.
 

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Agree with 50gary.

Put your finger over the outlet and keep it there. Pump the lever.If you are not feeling pressure then there is something wrong with the MC.



If you get pressure just re connect the banjo bolt and the system should bleed easier for you.



I also agree with abes_CW. Tying back the lever overnight is only something you do when you are finished and maybe have a bit of spongieness still.
 

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Sometimes it takes 500 squeezes of the brake lever to get pressure. Holding your thumb over the output hole while squeezing the lever sometimes helps.


It takes me around 10 seconds and a few squeezes of the lever.
 

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One more trick to try in a pinch that works well for me is to rotate the handlebars so the banjo outlet of the M/C is below the little holes in the bottom of the reservoir. This is so any air will rise and burp out the little holes in the M/C. If you pull a fraction of an inch of lever you can see the air bubbles escape. Note that the level of fluid in the reservoir has to be pretty low in order to get the banjo below the little holes, so you will probably have to remove some before rotating the handlebars.



Air will naturally move upwards in the lines; if the M/C banjo is the high point any air will collect there. The above method lets the air out by making the little holes the highest point in the system. You have to just slightly pull the lever though to let the air out. Once there are no more bubbles rotate the bars back and fill the reservoir.
 
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