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I have an 83 gs750e im putting together. I hooked up the front brakes fine. But I cant get any fluid to go through the master. I fiiled it up put cap on and pumped it, nothing. I disconnected the line just to see if any was coming out, nothing. So took it off the bike, cleaned it out pretty good with an air hose, tried it again and nothing. I took another master cylinder I had off an 450 parts bike that was basicallt the same. i got nothing out of that one either. Is it something Im doing wrong, I know how to bleed brakes on a car and was thinking the same, i dont know. Any ideas?
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you need to bleed the master cylinder!
when it is full of air it wont prime it self you move the lever and it just moves the air back and forth.
remove the line from the master cylinder
pull the lever all the way in
put finger over the hole the line connects to and let lever out slowly all the way
pull lever back in and as you are pulling in the lever pull finger off hole
place finger back on hole and slowly let lever out again.
this will make it develop a vacuum in the cylinder and suck fluid in. normally you only have to do this a couple times to prime the cylinder.
connect the line back up and turn the bars so that the master cylinder is pointing down some, (the discharge port needs to be lower than the port in the reservoir) slowly work the lever and watch the bubbles come out of the port in the reservoir.
this is working out the rest of the air in the master cylinder and the banjo bolt.
I just replaced my master cylinder and it took three priming strokes to get the master cylinder to push fluid and about 30 pulls to work the air back out through the master cylinder.
do not try to push the air bubbles out through the calipers, it wont work, the air bubbles always rise to the high point (master cylinder) you just need to work the lever and change the angle of the cylinder to allow the bubbles to find their way out through the reservoir. -
bleeding brakes
ok, i tired what you said, but i still have no brakes and the lever moves easy. after i hook up the line and i pull the lever a few times, the fluid just shoots out the top. i do see bubbles, but nothing is still working. when you said one hole has to be higher than other, which one. the one closer to the line or further one. All i got so far is a big mess of brake fluid all over my bike.Comment
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this thread is pretty close in topic to yours, with some good tips included.
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bleeding brakes
ok, i kind of got some fluid to move. the brake lever is still loose though. the pressure wont build up. if i pump it alot, it will build up and the lever will get a little bit stiffer, but when you let go for like 5 seonds, it gets soft again. i was trying something, i pulled the lever in and squeezed the rubber line with a pair of pliers gently so it would stop the fluid. I let go of the lever than the line than pulled in the lever. it was solid, the brakes felt like they should feel like this. the front wheel was locked. but when i let go of the lever, the brakes were loose again. i know the problem is in the master cylinder. I cant seem to get this vacuum process to work right. I was trying everything I know today for about 3 hours and a couple friends tried to help but they couldn't understand why it didn't work either. also, is there a certain process to bleed the forks, because my bike has the anti-dive setup with the brake-lines going to the forks also. I really need help and need to get this done.Comment
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Get a brake vacume pump.
Get one of those brake vacume pumps. I use it every few years to replace all the fluid in the front and rear. The first time I did it the rear system took some heavy suction to get it cleared out. Yours might be slugish as well. No matter what the condition even if you have air in the system you can flush it all out with a $20.00 pump. As long as the resivoir is kept full you wont have any problems. After sucking a few resivoirs full of new fluid through the line you can be really sure that the system is flushed and air free. Even if you see a few small air bubles going past it is probably just sneeking past the threads of the bleeder valve and not coming from the system itself.
Works wonders for getting the caliper pistons to move back without forcing the old fluid back up to the resivoir as well.Comment
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it's soft because there is air in the lines, you need to get it out. you can have someone help you with this, or do it yourself as I did, but it's a lot ot juggle.
pump the MC until it feels tight and HOLD IT IN, (10 times is fine) then with a hose on the end of the bleeder screw going into a bucket, 8mm on the hex, undo the bleeder screw ~1 turn and you'll hear it hiss air out. Close the bleeder screw and start pumping the MC again. Loosen the bleeder screw and again you'll hear it hiss. Eventually fluid will start to flow out the bleeder through the hose. It usually flows for about 2 seconds before it moves backwards. Bleed it until you see no air bubbles.
Remember the key is to keep the brake lever held in when you open the bleeder screw.
~AdamComment
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