Question on brake bleeding

I'd like to flush my old brown brake fluid and replace with new. I've been reading some old posts to get an idea of the easiest way to do this. What I plan on doing is attaching a MityVac pump to the bleeder on the caliper and pumping it a little to create a vacume. then opening up the M/C and sucking some of the old brake fluid out with a turkey baster and adding some new fluid. Then open up the bleeder untill the fluid starts to come out and just add new fluid to the M/C as it goes down, not letting it go down too much and let air into the line. Once I see new fluid come out the bleeder then close it, top off the M/C and I'm done. Move onto the other caliper and do the same. Starting with the caliper furthest away from the M/C. Does that sound right and am I missing any important details here? Am I right in thinking I wont have to touch the break lever at all doing it this way? I was told that unless the brake lever or pedal is pulled in or pushed down theres no connection to the M/C. This is the first time I try this.

Post edited by: cudaosix, at: 2006/08/22 16:58

Post edited by: cudaosix, at: 2006/08/22 16:59

it took me hours of bleeding with a vacuum pump. i used a electric pump and a t fitting and did both calipers at the same time. i did start from dry rebuilt everything though. id suggest you do as you say. one side at a time but i think you will have to give the lever a squeeze once in a while to keep things moving well...steve

if you do it the way you said you should not have any problems:P

On my 650B bleeding the front brake lines from completely dry was a piece of cake and I doubt I spent an hour on it. I don't know if I did it "by the book", but here is what I did.

First, after reassembling everything, I just pumped the handle until air bubbles stopped showing in the reservior.

Second, I use a length of line from the bleed valve on the caliper down into a small jar on the floor. Then I poured some brake fluid into the jar so that the end of the hose was submerged. This is important as it keeps air from entering the system from the bottom!

Third, I began the bleeding process. I put a 10mm wrench on the bleed valve and opened the valve then squeezed the handle and while holding it closed (next to the throttle grip) closed the bleed valve and then released the brake lever. Continue until no more bubbles appear (clear line into the jar makes this easy to see).

Also, make sure the brake fluid has not been shaken and has sat at least a day. The fluid will arreate when shaken or stirred resulting in air in your system the next day.

With two brakes do one side and then the next.

- Nate >>

Valuable advice from all of you. Thanks.

N0NB wrote:

On my 650B bleeding the front brake lines from completely dry was a piece of cake and I doubt I spent an hour on it. I don't know if I did it "by the book", but here is what I did.

First, after reassembling everything, I just pumped the handle until air bubbles stopped showing in the reservior.

Second, I use a length of line from the bleed valve on the caliper down into a small jar on the floor. Then I poured some brake fluid into the jar so that the end of the hose was submerged. This is important as it keeps air from entering the system from the bottom!

Third, I began the bleeding process. I put a 10mm wrench on the bleed valve and opened the valve then squeezed the handle and while holding it closed (next to the throttle grip) closed the bleed valve and then released the brake lever. Continue until no more bubbles appear (clear line into the jar makes this easy to see).

Also, make sure the brake fluid has not been shaken and has sat at least a day. The fluid will arreate when shaken or stirred resulting in air in your system the next day.

With two brakes do one side and then the next.

- Nate >>

This is pretty much how I learned how to bleed the breaks on a car. Glad to here the method is good on a bike also.

Yep, I just did my front brake the same way Nate described and it worked great, only thing I did different was I used a speed bleeder.

AzKZ650 wrote:

Yep, I just did my front brake the same way Nate described and it worked great, only thing I did different was I used a speed bleeder.

I used the Armstrong bleeder! :laugh:

- Nate >>

N0NB wrote:

On my 650B bleeding the front brake lines from completely dry was a piece of cake and I doubt I spent an hour on it. I don't know if I did it "by the book", but here is what I did.

First, after reassembling everything, I just pumped the handle until air bubbles stopped showing in the reservior.

Second, I use a length of line from the bleed valve on the caliper down into a small jar on the floor. Then I poured some brake fluid into the jar so that the end of the hose was submerged. This is important as it keeps air from entering the system from the bottom!

Third, I began the bleeding process. I put a 10mm wrench on the bleed valve and opened the valve then squeezed the handle and while holding it closed (next to the throttle grip) closed the bleed valve and then released the brake lever. Continue until no more bubbles appear (clear line into the jar makes this easy to see).

Also, make sure the brake fluid has not been shaken and has sat at least a day. The fluid will arreate when shaken or stirred resulting in air in your system the next day.

With two brakes do one side and then the next.

- Nate >>

Nate, just so I understand. You opened the valve then squeezed the lever, held it closed then closed the bleed valve and let go of the lever? Reading my Clymer I understood it said to first squeeze the lever and hold it closed then open the valve. Once some of the fluid comes through close the valve then let go of the lever. Or does it not really make a differance? Does it not matter if you open the bleeder valve without sqeezing the brake lever?

The Clymer also said to empty the line first then add new fluid and bleed. I wanted to just squeeze out some of the old fluid and go adding new fluid into the reservior until what comes out of the line at the caliper was clean. Would it work fine doing it that way instead of draining the old fluid first? It also said to install the reservior cap while doing this. Can I just leave it off while I bleed the brakes?

Post edited by: cudaosix, at: 2006/08/22 23:53

Post edited by: cudaosix, at: 2006/08/22 23:57

Post edited by: cudaosix, at: 2006/08/23 00:12

I don't recommend using a Mityvac. I have one and have never been successful in bleeding a system with it. Seems to always suck air from somewhere. I have a pressure bleeder that works great on cars, but doesn't work all that well on my KZ650C, which I think has different master cylinder from yours. I would use the turkey baster to remove as much fluid from the MC as possible, refill it and bleed as detailed in your Clymer manual. Be sure to keep the MC topped off.

cudaosix wrote:

Nate, just so I understand. You opened the valve then squeezed the lever, held it closed then closed the bleed valve and let go of the lever? Reading my Clymer I understood it said to first squeeze the lever and hold it closed then open the valve. Once some of the fluid comes through close the valve then let go of the lever. Or does it not really make a differance? Does it not matter if you open the bleeder valve without sqeezing the brake lever?

You'll get somewhat coordinated with it after a few tries as to how it feels. By the time I was done I was probably opening the bleed valve as I was beginning to squeeze the lever. To get the air out quicker I would have the bleeder open through the entire lever stroke. The bleeder needs to be closed snugly (hence my use of the wrench) before the lever is released so the fluid will be drawn from the reservior and not the container on the floor.

The Clymer also said to empty the line first then add new fluid and bleed. I wanted to just squeeze out some of the old fluid and go adding new fluid into the reservior until what comes out of the line at the caliper was clean. Would it work fine doing it that way instead of draining the old fluid first? It also said to install the reservior cap while doing this. Can I just leave it off while I bleed the brakes?

I think you would be better off to simply do as you've planned. Maybe suck out most of the old fluid out of the reservior with a syringe and then be sure that plenty of fluid is kept in the reservior so air is not drawn into the system. Pump it through until it's clear and maybe a little more for good measure.

As for the reservior cap, you'll be adding fluid too often to remove it and reinstall it that much. Plus, you need to be able to easily see the fluid level so air doesn't enter the system (do you get the impression that everything is done to avoid air at all costs?).

Once you do it, you'll find it's not that bad. Right now I'm working through setting the valve clearances on the 650B. Like brake bleeding and fork seal replacement, the second will be easier than the first.

- Nate >>

While on this subject. I've rebuilt my MC with new seals etc. Buggered if I can get a solid feel to it! Works OK on the road, but awful spongy feel to it. I note the "don't bother putting the cap on and off", so here's the question:
The Aussie Z900 MC an all alloy unit, and looking down into it there are 2 bore holes in the base. Now, when you squeeze the lever, you get a little fountain of fluid squirting up from one of these holes. Maybe silly question, but should this happen?