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I was working on my brake system today (front brakes), and had the whole thing drained, and put in a hydraulic brake light switch. I bled the whole system starting with the master cylinder (using my thumb on the hole), then bled at the banjo bolt from the master cylinder, then bled the incoming banjo bolt for the split, then the first bolt, then the second, then each of the bleeders on each caliper seperately. It seemed like I got all the air out, and there was plenty of fluid coming out of the bleeder valves on the calipers (with absolutely NO air in them). So I thought I had the whole thing done. Tookk the bike for a quick spin, and I still have almost no pressure in the system. The brake lever is not activating the brakes until about 3/4 of the way in... which means my brake light switch is not activating until then either (due to the fact that its hydraulic now). Anyways... I can't figure out what the problem is... does anyone have any pointers on how I can get this done better? Until I drained the system today the brake pressure was great... I could barley touch the lever and the brakes would activate. I can't stand it how it is, and it's probably not safe. Any pointers would be great. Thanks.
 

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you can tell if there is air in the system,if you pump the brake lever and the pressure increases then there is air in there
did you bleed just using a pipe from the caliper bleed nipple? if so did you keep the end of the pipe submerged in brake fluid?also did you tighten the bleed nipple when the brake lever was pulled in the back position
you need to know if its air or a seal really
good luck
 

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I bet the problem lies somewhere with the new switch. Either there is a possible air pocket there, or the switch itself requires excessive fluid transfer. If the piston that actuates the switch requires too much fluid before it actuates, it will eat-up a lot of your lever travel even if there is no air. Good luck.....
 

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I got TTTTWWWOOOOO WORDS for ya.....Mighty Vac. It's the only way to bleed your brakes right. One will cost you about 40 bucks at the Auto Parts store.
Bones
 

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A mightyvac would work, but I always just used a foot of clear tubing of the bleeder nipple diameter attached to the nipple. Put the 8mm wrench on the nipple with it closed, pump the lever until it gets stiff with pressure and then hold the lever in, then turn the 8mm wrench to open the nipple to let out the offending air, then close it quickly. I'm able to do both sides in 20 minutes or so and use about 1/4 of the bottle of brake fluid.

I think it is unlikely the switch is defective. It is activated by increased fluid pressure and with the air in the system, it isn't tripping until, as you said, 3/4 lever travel. Get the air out and it will work like a dream.
 

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Another good trick that I just learned is too bleed as usual (written by Simon) then tape the brake lever to the handle bar, as if you are applying the brakes, and leave it that way over night. Any small amounts of air in the master will come out. This made a friends brakes very stiff. So compress the lever and fix it that way, and see how it is in the morning.
 

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Originally posted by Rbike:
Another good trick that I just learned is too bleed as usual (written by Simon) then tape the brake lever to the handle bar, as if you are applying the brakes, and leave it that way over night. Any small amounts of air in the master will come out. This made a friends brakes very stiff. So compress the lever and fix it that way, and see how it is in the morning.
<font size="2" face="Verdana, Arial">Hmmm... I never tried that specific trick... but I do know that after you assemble a dry system and fill it, you will *always* need to let it sit for a while after the initial-bleed and come back to it later to bleed it a second time... some of the air bubbles get trapped and broken up into such tiny little pockets that it's just impossible to complete the job til the whole thing "settles" a bit. Also, I nkow it's messy, but I've never been able to *completely* bench-bleed a MC master-cylinder... it always seems like I hafta crack the banjo-bolt there (with a rag wrapped around to keep fluid off the rest of the bike) before the system is completely bled. Rbike's method might alleviate all those problems all with one shot.
 

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The only good way that I've found to bench bleed a master cylinder is to ruin a line by keeping the banjo end and cutting off the other end. Leave it long enough to put the cut end back into the master cyl resevoir. This way you are just pumping the fluid back around and you don't need to keep refilling it. Also change the length of stroke while bleeding, some slow full strokes alternating with some short fast ones.

Even after all this you will still have to bleed the banjo fitting if you haven't messed with any other part of the system. If you are putting on all new stuff then you can skip the banjo fitting and just bleed the system as usual.
 

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I bled my brakes yesterday and got rid of some really mucky fluid in there, I used that mighty vac one man bleed gadget which worked a treat, but after I bleed the entire system I always tye the front lever shut with some string and put a brick on the rear pedal, leave it overnight, then in the morning you gently undo the string whilst tapping the lines and the cylinder. By allowing the bike to sit overnight the air bubbles naturaly rise up and as you tap and let the lever out they get expelled out of the system, it works a treat!!!
 
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