How to: Bleeding The Brakes


Smells of Raw Fuel
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Western Maryland
Bleeding your brakes is quite easy and very important. Air in the lines can cause brake fade and failure, which can result in severe injury. However, bleeding the braking system is not to be used as a "quick fix" for other problems. Proper understanding of the master cylinder and brake caliper units is paramount. Brake bleeding is normally reserved for AFTER the braking system has been overhauled and/or rebuilt. These systems work in conjunction with each other and should be serviced, properly, together. Do Not overlook one for the other. Though separate, these units should be treated as one.
NOTE: Read manufacturer's suggested DOT fluid rating and NEVER mix two different types of brake fluids. If you plan to bleed your brakes, bleed them entirely and replace fluid from a new, unopened container. Only use brake fluid!! Not oil, not hydraulic fluid, ect., only brake fluid.
Brake fluid is a dangerous substance. DO NOT let it come into contact with painted surfaces. Immediately clean up any spill and wash hands thoroughly. Keeping a "more than normal" clean area when working with brake parts is very important!
Makes sure you read this in it's entirety and thoroughly before beginning.

This will cover the standard procedure for bleeding brakes. Both vacuum bleeding and "oil can" bleeding is covered at the end of this tutorial. Ok, lets begin.

First, read what type of DOT rated fluid you will need. It is on the master cylinder (m/c) reservoir cover or in your motorcycle owners manual (mom).
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Next, you will want to reset the brake m/c position. When you open the m/c fluid will spill everywhere if the m/c is not level.
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Place the bike on it's center stand and/or level the machine as much as possible. Using a 10mm socket, loosen the bolts enough to move the m/c level, slighty retighten to hold it in place.
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Now, remove the 4 bolts that hold the m/c cover on. Note: I have replaced my original bolts with new, stainless steel M5 / 3mm, tappered allen head. The originals will strip!
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Check the fluid level of the m/c and clean it out if necessary.
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Find a sutible container to hold brake fluid in.
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The object of bleeding the brakes is to remove air from the lines, thus you want to push fluid thru, and out of, the system. To do this you must attach one end of a tube, preferably clear, to the bleeding nipple...
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...and submerge the other end in a container full of brake fluid.
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This will allow air to exit the caliper and be forced under the fluid level. Since the end of the tube is submerged, air can not go back into the system once the tube is full of fluid. Try to keep the end of the tube submerged under the fluid level. If the tube comes out it is ok, just make sure that the fluid does not flow back into the system, bringing air with it. This can be avoided by tightening the nipple during the bleeding process.

4 step process here. 1) You will be pulling the brake lever in. 2) opening the bleeding nipple and pumping the lever. 3) retightening the nipple (just snug). 4) Releasing the lever.

So, using a 5/16 wrench, pull the lever in...
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...and open the nipple. Do not completely remove the nipple. Just "crack" it open enough to allow fluid to flow out. Pump the lever a few times. The tube will fill with fluid and go into the container. Again, try to keep the tube submerged and do not let the fluid fall back into the caliper letting air in. Make sure you have fluid in the tube at all times. This will insure fluid does not flow back in followed by air. NOTE: Because the tube is on the nipple you will need to use the open end of the wrench. Opening the nipple with the wrench, with the tube on, is a pain, but after a few times it becomes easier to work around.
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Then tighten the nipple while holding the lever in and then releasing the lever. Since the nipple is on top of the caliper, and the tube needs to curve down, tightening the nipple each time prevents fluid from falling back into the caliper and letting air in. It also keeps you from having to constantly pump the lever in order to prevent air going back in. Believe me, you will understand once you do this.
You will need to do this several times.
You want to do a little "dance". So it's "lever, nipple, pump-pump, nipple, lever", repeat.
Pulling the lever in pressurises the system, opening the nipple lets air and fluid escape, closing the nipple keeps fluid and air from going back in (Kind of a secondary safety), then release the lever. You may want to pump the lever a couple times to push air down to the nipple.
NOTE!!!! make sure you are watching the m/c reservoir. DO NOT let it run empty. You will need to keep adding fluid throughout this process. If you let it run dry, air will go into the system and you will have to start over.

What am I looking for?
You want to get all the air out. To know when this has happened you will, 1, see no more air bubbles coming out of the nipple and through the tube. And 2, the brake lever will no longer feel "spongy". If you have to "pump" the lever to build-up pressure, air is still present in the system. Everytime you pull the lever in it should feel nice, smooth, and be the same "pull" pressure each time. Remember to tighten the nipple each time. Do not "wrench" it tight, just snug it. This makes it a little easier to manage. Especially if you have to stand up and refill the reservoir.
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Once all the air is out, no more bubbles and no spongy feeling, top off the reservoir with fluid.
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Then put the cover back on and tighten the bolts.
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Collaborative article written by members of / 2011
Last edited:
After you have completed these steps you can remove the tube. NOTE: Make sure the nipple is tightened before removing the tube.
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Be sure everything is tightened correctly!!
Make sure you properly clean up all the brake fluid, especially on painted parts. It will eat right through it!!! If you get fluid onto the rotor remove it with brake cleaner. Brake fluid can contaminate the brake pads.
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Be sure to readjust the lever and m/c at the handle bars, tightening the 2 bolts securely.
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And you're done. Good job!!
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These are important tips, so please read!!

Only use new brake fluid with the correct DOT rating.
Spongy brakes usually means all the air is not out of the system, however, old brake lines will also cause a spongy feel. Replacing them with new lines is a good idea. You want consistency each time you pull.
If you have to "pump" the lever to get it to a nice feel, air is still present in the system. It should pull and return the same everytime.
Be careful when you take the machine out the first time. Go slow and check, check, check!!!
If you see fluid coming from anywhere, look for a leak and retighten if necessary.
Check the brakes the following day. If the brakes are noticeably more spongy, or need to be pumped to build pressure, you might have a leak caused by a bad line or a faulty master cylinder.

Alternative ways to bleed the brakes:
There are also several alternative ways to bleed the brakes.

Lever Type Oil Can:
An oil can bleeder is an easy way to remove the air. Since air rises to the top you can force the air from the caliper to the m/c. This is called "back bleeding". So, if you have replenished the system with new fluid, this is a good way of final bleeding. Or, upon checking the fluid, and it is low, this is a good way to fill the m/c reservoir and bleed the system at the same time.

Lever type oil cans can be bought just about anywhere. Be sure to use a new, unused can. These are made for oiling parts, so be sure there is no oil in the one you are using. The oil can damage the brake system.

Note: This needs to be done with a very low level of fluid in the reservoir. You will be forcing fluid from the caliper into the reservoir.
Fill the oil can with new, fresh brake fluid. Using a piece of clear tubing, the same as used in conventional bleeding, attach one end to the oil can and secure it with a small hose clamp. The other end will be attached to the bleeder nipple and also secured with a hose clamp.
Attach the end of the tube, using the clamp, to the nipple. Slowly open the nipple a 1/2 and very slowly pump the lever on the can. Squeeze slowly. If you forcefully pump the can you will overflow the reservoir and "fountain" brake fluid.
This will force the air to the top and out of the m/c reservoir. This will also be adding fluid to the system, thus filling the m/c reservoir. If all the air (bubbles) have not been removed, and the reservoir is full, you can use a small turkey baster to carefully remove some fluid and then continue.
Once all the air bubbles are out, and the reservoir is filled, tighten the nipple, then remove the clamp and hose. Replace the reservoir top, ensure everything is properly tightened, and clean up spilled fluid. Note: Be sure to label the oil can, and baster if used, with a "For Brakes Only" label, or something similar, to ensure it is not accidentally used for other projects or placed in the kitchen.

Using the MityVac Vacuum Bleeder:
You will need the MityVac vacuum Bleeder pump, short hose, catch reservoir, long hose.
1. Put your 8mm wrench on the bleeder, but leave the bleeder closed.
2. Place the long hose on the bleeder.
3. Fill the brake reservoir
4. Pump the handle about 20 times to build vacuum.
5. Use the 8mm wrench to open the bleeder.
6. Air bubbles and fluid start to flow out. When the flow begins to slow, close the bleeder.
7. Repeat this process, steps 3-7.
8. After you close the bleeder, after bleeding the second time, you should have good pressure at the lever.
Note: Due to the air gap around the threads of the bleeder, you'll likely see bubbles even when all the air is out of the system. This can be lessened by putting grease around the bleeder or teflon tape, but I don't find it necessary to get a proper bleed. Just be aware of this.
This is a very simple way of bleeding the brakes.
Warning!! You should not use vacuum pumps with "Speed Bleeding" nipples.

You can also do a "Finishing Bleed" this way:
1. Remove the cover on the master cylinder.
2. Remove the caliper.
3. Hold the caliper with the piston facing down.
4. Gently Squeeze the piston into the caliper bore.
5. Operate the brake lever to push the piston back out. Not too far, of course.
6. Repeat 4 and 5 until your arms fall off.

As you do this procedure, you will see air bubbles in the master cylinder reservoir even if you did the more traditional bleeding method for hours. The caliper piston will not blow out when you operate the brake lever. In fact, you can operate it several times for each cycle of the procedure.

You can also do this procedure from time to time without having to open the bleed screw if you suspect some air got into the system, which can happen in a rough ride if you apply the brakes and the tiny hole in the master cylinder reservoir gets unported.

A caliper rebuild how to.
Collaborative article written by members of / 2011
Last edited by a moderator:
Thanks for putting together such a thorough detailed how-to. If I could I'd like to offer a third variation, sort of between the nipple-pump and MytiVac techniques (because I've never been completely successful with a MytiVac and the back-and-forth of the nipple-pump drives me nuts). I connect an extra-long clear tube from the bleeder to the inlet of the MytiVac catch reservoir, and hang the reservoir up by the handlebar (usually with a piece of stiff wire bent fof the purpose). I then crack the bleeder and leave open while pumping the lever slowly and refilling the master cylinder as needed. The vertical clear tube makes it easy to see the bubbles and when they stop, and you don't have to do the back-and-forth or worry about the tube coming out of the jar or tipping it over. I also use this method on car brakes, so I don't need an assistant to pump the pedal while I work the bleeder.
Very good thread. The only thing I might suggest is in the first description, step four. I pump the lever to get some pressure then hold the lever, open bleeder. As you hold the lever it will pull in to the bar. Don't pump the lever with the bleeder open. This pulls fluid and air back into the bleeder. Close bleeder. Now again pump lever to get pressure, hold, open bleeder, close bleeder. Repeat as many times as needed.
Pump, hold, bleed, close. repeat.

Good summary here:

I have not changed over, though it appears you'd have to be really careful to chase the DOT 3/4 from the system before introducing the DOT 5, since they combine to form a sludge. It would be nice to have brake fluid that wouldn't eat paint. I don't know that I ever work the brakes hard enough that the improved temperature performance of DOT 5 would be required.
DOT5 was all the rage back in the late '80s, today not so much. The conventional DOT3 and 4 fluids have been improved to the point where I don't think there's much of a performance difference anymore. I converted one of my bikes over to DOT5 back then, my SR500. It required I flush the system with alcohol to thoroughly clear the DOT3 out. It works fine but so does my 650 with essentially the same brake components and using DOT3-4. I wouldn't bother with the swap again.

DOT5 costs more and is harder to find. The benefits are it doesn't eat your paint and requires less changes because it doesn't absorb moisture like normal brake fluid.
Everything I own has DOT 4 in it, no need to buy more fluid. I flush my brake systems every time I change a tire (less than a year currently) and always buy the little bottles, so I'm popping a fresh lid every time. I put my waste in with my oil drain tank for disposal. We bleed some aircraft brakes (non-powered) with a circuit bleeder, were a hose runs from the brake back up to the resevior, and you just pump to your heart's content, and keep the resevior topped up. Works pretty good, but I've learned over the years I always do the best if I burp all the banjos, as well as tie down the lever overnight.
Great article. What size clear tubing are you using to bleed nipple? 3/16?

Also, what fluid are you submerging the lower end of the tube in? Is it the fluid you've already drained, or a fresh pool?


Whatever size fits best, 3/16" is probably good for this brake. I have a couple sizes because some of my bikes have larger nipples (the Euro bikes). When I change my fluid, I suck most of the old stuff out of the reservoir first (no sense pumping all that through the system) and pour fresh stuff on top. That old stuff goes in the catch bottle.
The size hose is whatever size fits snuggly on the bleeder.
With the hose in a small jar at the bottom of the jar, as you bleed the brakes the jar fills with fluid. This is the fluid the hose rests in.
You can, if you want put some fresh fluid in the jar first.

Wrap a layer of Teflon tape around the nipple threads before you begin. This keeps air and fluid from getting past the threads. It is the only way to use a Mity Vac.

Throw a thick towel over the tank before you start.

Use an ear bulb with a short length of aquarium hose forced over the end to suck out the dirty fluid from the reservoir. You might be able to see dirt particles so suck these up.

After you have flushed the dirty fluid from an old bike the new fluid will grab contaminates from every nook and cranny of the system. In a week the fluid will be discolored again and eventually need reflushed. Once a year from then on.

Start now and make up a brake kit with all the little hoses, Teflon tape and fittings in one box. I have one I started years ago and it has been a valuable box of 'tools' for all sorts of brake fluid work.

If your like me with just a hose in a jar it will get knocked over and spilled a lot. Untill I got the Miti Vac I used a bleeder like this. The magnet holds the jar up and away from things that will spill it.


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