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Brakes Bleeding

Brake & Clutch bleeding trick - COG digest #2349, Jan. 29, 2001

I would like to share brake and clutch bleeding trick that I picked up off the Transalp list. I had changed the fluids in both my Connie and my Alp's brake and clutch systems last summer and despite repeated efforts with a mity-vac and standard bleed methods I was never satisfied that I had full brake or clutch. A person came on the Alp list with a similar complaint and someone else suggested pulling back on the brake and using rubber bands to keep it that way then walk off and leave it overnight. I did this to the Alp's brakes and the Connie's brakes and clutch. I gained at least an inch of lever pull on both bikes and the Connie's clutch has never been better. I can be lazy with that 1st to 2nd up shift and it snicks right in. Try it; its easy no cost and worth the little effort.

COG Digest 2350,  Jan.30, 2001

As a former hydraulic tech, let me share this: No matter how much you bleed the brakes, tiny little air bubbles will stick to the inside surfaces of the lines. By depressing the lever overnight, you are forcing the bubbles back into solution. They could come back out of solution later! The best trick I have found is to take the major components loose so that you can hold them in a way that all the lines and components go up hill. No level or back curves. Gently tap along the length of the lines with the handle of a screwdriver. Work your way from bottom to top a few times. Take your time. The bubbles break loose then float upward slowly. Then work the handle of the master cylinder back & forth lightly and quickly. If you see inside, you'd see the little bubbles coming back up into the master cylinder. Now reattach the lever assembly and check lever feel. I have found this technique can be involved and time consuming when bodywork is involved. But it has solved many a spongy lever problem on many bikes. It gets the air out for good. If you're really anal, as I can be with my machines, Put the fresh brake fluid in a jar and pull a vacuum on it and let it sit for a few hours before use. You will de-areate it pretty thoroughly before putting it in the system. As you pull the vacuum on it, it will look like you opened a soda pop! Thanks again to all the posters here! I'm really enjoying the list!
Rich Maund, Rich's Cycle Upholstery, Chesapeake, Va.

COG Digest 2352 Jan. 31 2001

Thought I would share another method with you. Try it if you wish, it works very well for me.
Buy the best pump style, hydraulic oil can you can find and dedicate it solely to brake fluid. Buy fresh fluid, fill the oil can and attach the spout of the can to one of your bleed screws via a short length of clean, virgin tubing, purging the air from the tubing before you connect it. Remove the top of the master cylinder and put somebody up there with a big syringe on stand-by.

Open the bleeder screw on your caliper and SLOWLY begin pumping the new fluid from the oil can, into the caliper, uphill through the brake lines and into the master cylinder. As the master fills up, the person up top sucks the old fluid out and the new, airless fluid fills in from the bottom and continues raising the level. Keep doing this until the old fluid is out of one caliper, then switch to the other side and repeat. Works for any system, and only takes a few minutes.
Ronnie Lyons, #4150, Meridian, ID

(Original source no longer available)

The key to vacuum bleeding is elimination of air intrusion around the bleeder fitting screws. I have started putting anti seize on the bleeder screws to seal them. You can also put some axle grease around the base of the bleeder. Works great. I also bought a $65 suction bleeder from Griot's Garage which is absolutely wonderful compared to using a Mity-Vac. You just pump it up (vacuum) and walk from wheel to wheel, hook it up and open the bleeder. It also holds a couple gallons of spent fluid. Comes with a bottle that can be used to keep the master cylinder full.

SOHC Honda Digest 2931

Here's what I do to make the process easier, its my own version of a speed bleeder.

Go to a fish store and you can fine these gang valves that are used in fish tanks to prevent water from flowing back into the air pump in the event of power failure.

Well, splice the tube you use to drain your brake fluid and put the gang valve in the middle of the line. Then all you have to do is open the bleeder, pump your brake and make sure to top up the master with fluid so you don't pump air through it.

This is the best thing in the world actually,  I use it to do the brakes on my car bike, friend's cars, everything.

Oh! and the valve only costs $1.50, but I'd get the sturdiest one you can find. These things are supposed to have air flowing through them, not oil, and they aren't built to block the flow under high pressure, but mine works just fine.

Article By: David J. Morrow

August 2001

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