Well, I'm almost finished restoring a 1983 CB650SC Nighthawk. The last thing to do (as far as I know right now) is bleed the brakes. The calipers, master cylinder and break lines were toast. I got new caliper pistons and seals. I got a rebuild kit for the master cylinder. I got new brake lines, banjo bolts and washers. After installing everything I have tried to bleed the brakes. When I turn the bleeder screw nothing comes out. I've tried the traditional way of squeezing the brake lever a little and holding it; then opening up the bleeder and squeezing the brake lever all the way and holding it and then closing the bleeder. Nothing comes out, no air and no brake fluid. I then got some "speed bleeders". They are suppose to let you open the bleeder and then keep squeezing the brake lever until all the air is out. Nothing comes out, no air and no brake fluid. If I remove the bleeder screw, brake fluid will ooze out. With the bleeder removed and if I squeeze the brake lever, brake fluid still just oozes out. All during the process, I make sure that the reservoir is full of brake fluid. I'm so close to riding this bike I can taste it. I've even thought about riding with only the rear DRUM brake...not a good idea. I just need to get the front brakes bled...what a pain. Anyone know the secret?
kinda sounds like you're not getting any pressure from the master. seems like it would ooze just from gravity down the line. it should almost squirt out when you squeeze the lever i think
Some time ago MisterMike mentioned a method using a modified master cylinder cover and a vacumm pump. If I remember correctly he mentioned puting an adapter on the master cover allowing you to connnect it to the vacumm pump. you could then suck the fluid in through the bleeder up to the master. Lets see if he chimes in. It sounded like a fool proof method considering any air would be forced out by the fluid on its way up to the master.
if there is any air in there you will have no pressure at the lever. starting from scratch it can be a little tricky to get all of the air out, it will hide in every little kink/bend. Here's a trick. Get a syrenge (sp) with a peice of tube. Fill it up and attach it to the bleeder valve. Push the fluid in from the bottom to fill it. If it is already full, like it seems, then do the opposite, with the bleeder open, suck the fluid through the system from the bleeder valve. This will force the fluid to work through the system, and pull most air bubbles with it. After a few master cylinder fulls, you should have enough pressure to bleed the brakes normally. Also, tap on the brake line lighty to free any trapped air bubbles.
I've raced motocross for 15+ years and had to bleed brakes at least a few times a month from scratch. This works very well.
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note: just make sure to watch the level of the master cylinder, it will empty pretty quickly. Nothing like not paying attention and sucking a full master cylinders worth of air into the system.
Not that I have ever done that...
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Motohead, This is driving me crazy. What is a syrenge (sp) and where would I get one? Is this for the brakes or for me? I do have a great big hammer that is looking like the tool of choice more and more. I'm hoping to get this bad boy on the road this weekend.
A syringe, AKA the plastic tube that they attach a needle too to give injections. Usually find a big one somewhere that they sell farm/ranch supplies, IE stuff for taking care of livestock. Then just get a piece of the correct size rubber vacumm line at an auto parts store to slip over the end the needle would go. Cheaper than a vacuum bleeder, does the same thing.
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Thanks guys. I went to a medical supply place and got a 60cc syringe. You can inject some serious stuff with this. I put a tube on the syringe and sucked up some brake fluid. Then I put the other end on the bleeder. I pushed all of the brake fluid from the syringe through the bleeder up into the master cylinder. I did this on both front calipers several times and I still have no pressure when I squeeze the brake lever. I then tried bleeding them the normal way making sure I didn't run the master cylinder dry. I have repeated this process many times and still no pressure. I'm now looking for that hammer. Not sure what to do next.......
I also suspect the master cylinder. Did you lightly hone the inner cylinder? What exactly did you do when performing the rebulid? Which rebuild kit did you use NOS or aftermarket?
I got the master cylinder rebuild kit from "Old Bike Barn". I'm pretty sure it was an OEM rebuild kit. What does NOS mean? I didn't hone the inner cylinder. After I took the master cylinder off and took it apart, I cleaned it up. I used a old tooth brush to get inside the inner cylinder. After it was cleaned up I dipped the parts in clean brake fluid and installed them.
Bleed the brakes at the banjo bolts- Pump the brakes a few times , hold it in and release the pressure at the bolt that connects the line to the master cylinder - just make sure to cover your body work, tank, speed o meter and everything else - you'll probably have to do it a few times, but, it should work, if it doesn't you know you've got issues in the Master Cylinder.
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When I put the new lines on my ZX10R, it took freakin forever to start getting spurts out the bleeder. I mean I pumped until I couldn't squeeze anymore!. I don't know how much you pumped the lever. The guys got a point about the master, but didn't you say you rebuilt it?
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LOL, Drum brakes have to be bled too, I hated doing it on my Roadrunner, it had a leaky master cylinder and if I didnt remember to top it every 6 months or so I would be under it with my vacuum bleeder cursing and pumping.
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I was wrong...it was not a dream...it was a nightmare. I tried it again and now I'm out of brake fluid (more than a liter) and out of patience. I took the master cylinder off and I might have a shop look at it or I might see how far I can shot put it...
I took the master cylinder to a shop and explained everything that I have done. The guy talked and asked questions for awhile and decided I need a new master cylinder...yea that's going to happen. We went and got the main mechanic and again I explained everything to him. He also said it was probably the master cylinder. He took a look at it and said Huh...what is this? He took a flash light and looked into the hole where the banjo bolt goes in and said there is your problem. I looked and saw the rubber cup. It was either all messed up or I put the rubber cup and spring in backwards I went home and took it apart and sure enough, I had put it in backwards...I hate when that happens. After I put it in the right way I bleed the brakes, it took about three times for each caliper and what do you know...I now had brake lever pressure So hopefully I will put the bike back together and go on a ride. If that happens I'll post before and after pics. Thanks for all your help.
I thought air was blocking the flow. Also, It started to become personal. There was no way a master cylinder was going to get the best of me...yea yea...it did...
I went home and took it apart and sure enough, I had put it in backwards...I hate when that happens. After I put it in the right way I bleed the brakes, it took about three times for each caliper and what do you know...I now had brake lever pressure 
So hopefully I will put the bike back together and go on a ride. If that happens I'll post before and after pics. Thanks for all your help.
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