GenII Front and Rear Brake Fluid, Clutch Fluid Bleed/Drain

[Mythos]

Brake and Clutch Fluid Bleed and Drain

The brake fluid in brake and clutch systems is bled primarily to to rid the system of air that may have entered the system during maintenance procedures. Fluid may also be bled in order to change old, worn out brake fluid for new. In this case, the system is not drained but fresh fluid is added while the system is being bled. Proportionally, only a small amount of the old fluid remains with the fresh fluid.

In some situations (such as removing brake lines) it is desirable to drain all fluid from the system. The fluid may be purged completely simply by bleeding the system without replenishing it. In this case, the fluid in the system is displaced by air. The system will need to be refilled with new fluid and thoroughly bled until all air is eliminated from the system.

Air can be compressed much easier than brake fluid so the presence of air anywhere within a brake system reduces the internal pressure that is built when brakes are applied. Without maximum brake fluid pressure, the moving parts within the brake system will lack force which results in a loss of braking power. Air within the brake system will be notable by what is often called a “spongy†feel to the brake lever or pedal. Spongy brakes feel soft and the lever actuates more than usual.

Any small amount of water is also undesirable to have trapped within the system. Water does not react to compression like brake fluid and it will overheat at a lower temperature. Be careful to keep any water that might be used to wash a brake fluid spill from entering the system. Dust and dirt particles can contribute to clogs in the systems so take measures to prevent them from entering the the system through an open reservoir.

Fill fluid reservoirs to just below the maximum full line and NO HIGHER. Overfilling the reservoir can result in an excessive volume when the fluid gets hot and expands from application of the brake. Excessive volume may cause brakes to lock without warning. Excessive internal fluid may also cause fluid leakage.

DOT #4 is the grade of brake fluid that is recommended for the Hayabusas brake system. Brake fluids that are labeled for use in systems requiring “DOT #3 or DOT #4†are actually no different than those specifically labeled for use in systems requiring DOT #4. DOT #5 is a higher performance break fluid with a higher boiling point but if DOT #5 is used in systems designed for DOT #4, the fluid may leak past the rubber seals.

Brake fluid will etch many painted or plastic surfaces that it comes in contact with. Therefore, a pail of water and sponge should be kept prepared for the inevitable drips and spills that occur while working with the brake and clutch fluid systems. It is always wise to cover as much of the bike as possible with plastic to prevent damage from spatters that may occur without having been detected.

The pictures in this tutorial show the body panels and some other parts removed for ease of viewing. It’s not necessary to remove these parts although if they are removed, they are safe from potential brake/clutch fluid spills.

Tools:
pail of water and sponge
plastic
8mm box end wrench
1/4†clear plastic hose
empty bottle.
towel
phillips screwdriver
electrical tape
fresh brake fluid
vacuum pump tool

Front Brake Bleed

Set the bike vertical on a rear stand to avoid fluid spills.

1. Cover the entire front of the motorcycle with plastic to protect painted and plastic
surfaces from accidental spills and spatters of brake fluid. Leave the front brake fluid reservoir uncovered by the plastic.


2. Remove the rubber cap from the front brake bleed valve located on the right front brake caliper.


I wrapped a piece of tape around the hex on the bleed valve to protect the finish from the wrench (see next step).

3. Place an 8mm box end wrench on the bleed valve of the right front brake caliper. Slide a 1/4†clear plastic hose over the nipple on the bleed valve and place the other end of the hose into an empty bottle.

Quarter inch O.D. plastic hose that is used for water tubing on refrigerators works well for bleed hose.

4. Place a towel around the front brake fluid reservoir. Use a phillips screwdriver to remove the the two screws that fasten the front brake fluid reservoir cover.

I stretch a piece of electrical tape over the tip of the screwdriver to prevent damage to the finish on the screws.

5. Remove the internal front brake fluid reservoir cover.

6. Remove the rubber gasket from the front brake fluid reservoir.


7. Slowly actuate the front brake lever, pumping if necessary to build pressure in the system. Watch for air bubbles rising to the top of the reservoir fluid. Hold the lever pressed.


It’s possible for fluid to squirt out. To be careful, slowly pump the lever.


Watch for tiny air bubbles rising rising in the reservoir when the brake is pumped. When they stop, the master cylinder is bled but more air may be trapped lower in the system. To remove all air, continue to bleed as described below.

8. While squeezing the brake lever, turn the bleed valve one quarter turn counterclockwise. Squeeze the brake lever to the grip and hold to express fluid. Watch for air bubbles in the hose. Turn the bleed valve closed again. Release the brake lever.

9. Tap the brake lines and master cylinder with a solid object to dislodge any air bubbles that may be clinging to the inside of the system. Continue bleeding.

10. Repeat steps 7-9 four or five more times. The process is: squeeze/pump lever, open bleed, close bleed, release lever.

squeeze, open, close, release...squeeze, open, close, release...

If bleeding is not performed in this order, air can be sucked back into the system rather than removed.

Do not allow the fluid to level to fall to the bottom of the reservoir or air will be sucked into the master cylinder. Replenish the brake fluid by pouring fresh fluid into the reservoir. Continue bleeding until the fluid comes out colorless (old fluid is red-brown).

While air is bled from the system, watch for air bubbles in the fluid that is expressed through the hose.

Continue bleeding the system until the fluid is colorless and clear of air.

11. Repeat steps 7-10 on the left front brake caliper and the front brake system should be completely bled of air.

12. When the system is bled of air, fill the the fluid reservoir to just below the upper fill line (never fill the fluid reservoir higher than the fill line) and install the reservoir gasket and inner and outer covers(reverse procedure of steps 4-6).


Remove the plastic tubing from the air bleeder valve, install the bleed cover and tighten the bleed valve(s).

Front bleed valves tightening torque: 5.5 ftlbs.

I do not tighten the delicate threads on the bleeds quite that much. Approximately 4 ft pounds is good and carefully check for signs of leakage from the bleeds immediately after a test ride with hard braking.

Rear Brake Bleed

Set the bike vertical on a rear stand to avoid fluid spills.

Remove the frame cover from the tail of the bike.

Plastic and a towel may be placed over the surrounding area to protect against possible spatters of brake fluid from the reservoir under the tail frame cover.

13. Remove the bleed valve cap.

14. Place an 8mm wrench on the bleed valve. Attach a length of 1/4 inch tubing to the bleed valve and place the opposite end in a receptacle.

15. Use a phillips screwdriver to remove the two screws from the reservoir cover of the rear brake fluid reservoir. Remove the reservoir cover.

16. Remove the gasket from the rear brake reservoir.

17. Pump the rear brake pedal and hold it down.


Watch the reservoir for any tiny air bubbles that might rise to the surface of the fluid. If bubbles are observed, continue pumping. When the bubbles stop, the rear brake master cylinder is bled of air. The lower end of the system still needs to be bled.

18. While holding the rear brake pedal down, open the rear brake bleed valve one quarter turn. Press the brake pedal to the bottom of its throw as brake pressure is eliminated and fluid is expressed from the bleed valve. Watch for air bubbles in the hose. While still holding the rear brake pedal all the way down, turn the the bleed valve closed. Allow the rear brake pedal to return back to the top position.

19. Tap the brake lines and master cylinder with a solid object to dislodge any air bubbles that may be clinging to the inside of the system. Continue bleeding.


20. Repeat steps 18-19 four or five more times. The process is: squeeze/pump lever, open bleed, close bleed, release lever...

squeeze, open, close, release... squeeze, open, close, release...

If the bleed is not performed in this order, air or old fluid from the receptacle can be sucked back into the system rather than removed.

Do not allow the fluid to level to fall to the bottom of the reservoir or air will be sucked into the master cylinder from the empty reservoir. Replenish the brake fluid by pouring fresh fluid into the reservoir as you bleed.

Continue bleeding and replenishing fluid as described above. As the system is bled, watch for air bubbles in the fluid that is expressed through the plastic hose attached to the bleed valve.


Continue bleeding the system until the fluid is colorless and clear of air.

21. When the system is bled of air, fill the the fluid reservoir to the upper fill line (never fill the fluid reservoir higher than the upper fill line) and install the reservoir gasket and cover (reverse procedure of steps 14-15). Remove the plastic tubing from the air bleeder valve, install the bleed cover and tighten the rear bleed valve.

Rear brake bleed valves tightening torque: 5.5 ft lbs.

I do not tighten the delicate threads on the bleeds quite that much. Approximately 4 ft pounds is good and carefully check for signs of leakage from the bleeds immediately after a test ride with hard braking.

Clutch Line Bleed

Set the bike vertical on a rear stand to avoid fluid spills.

22. Cover the entire front of the motorcycle with plastic to protect painted and plastic
surfaces from accidental spills and spatters of brake fluid. Leave the clutch fluid reservoir uncovered by the plastic.

23. Remove the rubber cap from the clutch slave bleed valve.


I wrapped a piece of tape around the hex on the bleed valve to protect the finish from the wrench (see next step).

24. Place an 8mm box end wrench on the clutch slave bleed valve. Slide a 1/4†clear plastic hose over the nipple on the bleed valve and place the other end of the hose into an empty bottle or other receptacle.

Quarter inch O.D. plastic hose that is used for water tubing on refrigerators works well for bleed hose.

25. Place a towel around the clutch fluid reservoir. Use a phillips screwdriver to remove the the two screws that fasten the front brake fluid reservoir cover.
I stretch a piece of electrical tape over the tip of the screwdriver to prevent damage to the finish on the screws.

26. Remove the internal clutch fluid reservoir cover.

27. Remove the rubber gasket from the clutch fluid reservoir.

28. Slowly actuate the clutch lever, pumping the lever. Watch for air bubbles rising to the top of the reservoir fluid. Hold the lever to the grip.

It’s possible for fluid to squirt out. To be careful, slowly pump the lever.

You might see tiny air bubbles rising in the reservoir when the clutch is pumped. If you see this, pump the clutch lever until the bubbles stop. The master cylinder is now bled but more air may be trapped lower in the system. To remove all air, continue to bleed as described below.

29. While holding the clutch lever to the grip, turn the bleed valve one quarter turn counterclockwise. Fluid will flow through the hose connected to the bleed valve. Watch for air bubbles in the hose. Turn the bleed valve closed again. Release the clutch lever.

30. Tap the clutch slave cylinder, lines and master cylinder with a solid object to dislodge any air bubbles that may be clinging to the inside of the system. Continue bleeding.

31. Repeat steps 28-30 four or five more times. The process is: squeeze/pump lever, open bleed, close bleed, release lever.

squeeze, open, close, release...squeeze, open, close, release...

If the bleed is not performed in this order, air can be sucked back into the system rather than removed.

Do not allow the fluid to level to fall to the bottom of the reservoir or air will be sucked into the master cylinder. Replenish the clutch fluid by pouring fresh fluid into the reservoir. Continue bleeding until the fluid comes out colorless (old fluid is red-brown).

When air is bled from the system, watch for air bubbles in the fluid that is expressed through the hose.

Continue bleeding the system until the fluid is colorless and clear of air.

32. When the system is bled of air, fill the the fluid reservoir to just below the fill mark (never fill the fluid reservoir higher than the fill mark) and install the reservoir gasket and inner and outer covers(reverse procedure of steps 25-27).

Remove the plastic tubing from the air bleeder valve, install the bleed cover and tighten the bleed valve(s).

Clutch slave bleed valve tightening torque: 4.5 ftlbs.

I do not tighten the delicate threads on the bleeds quite that much. Approximately 4 ft pounds is good and carefully check for signs of leakage from the bleeds immediately after a test ride.

 

[Mythos]

Draining Brake and Clutch Fluid

The process of draining the front brakes rear brake and clutch are exactly the same as that for bleeding. When purging the system of all fluid, simply DO NOT add fresh fluid to the reservoir. Allow air to be sucked into the system as the fluid is purged. The system will be bled of air later when it is refilled with fluid.

When any of the systems is emptied completely, it is difficult to get the new fluid to flow when it is first added. In this case, I have found it convenient to use a vacuum pump tool such as the Mityvac.

Mityvac

I use this vacuum pump tool from my Advance Auto store for a refundable $50 deposit. It is pretty beat up but still gets the job done.

A vacuum pump can actually be used to suck fluid through the system to bleed and replace fluid as well as start new fluid in an empty system. They can be used to siphon any liquid and some can even be used to check engine compression and coolant system pressure.

 

[HOOKDADDY]

wow now how do we pinn this or is it

 

[GoldenChild]

Good Write up, this tool will make it even faster..Doesn't allow air into the system..



Motion Pro Brake Bleeder | MotoSport

 

[Mythos]

thanks, hope it helps some DIYers out there. I'd be willing to bet you could follow this for the GenI as well as the GenII. My Kawasaki is the same except it has a bleed valve on the master cylinders as well as the lower end of the systems.

Main thing is to make sure the reservoir is not filled past the fill mark. I have heard of a couple guys having a rear brake lock up from being over filled.

 

[cheferman65]

Nice write up Sir!

Why does your brake fluid look like a good amber syrup? Are you using old fluid?

Maybe just the pictures?

 

[Mythos]

Ahh, you noticed, cheferman. That last pic was taken before I bled much out or drained the system. I used the pic to illustrate filling the reservoir with fresh fluid after bleeding but in reality it was adding during the start of the bleed when most of the fluid is still the old stuff that was in there.

The brake fluid I used is just slightly yellow I think. You can't tell unless you look through a an inch or more of it. You are supposed to always use brand new fluid, freshly opened. I haven't had any problems using fluid opened a year or two ago. It may have discolored some though.

That is a good point to bring up because fluid that is old and unused could have been contaminated with condensation (water). Like I mentioned though, I never had an issue with that and I used my old, unused fluid to fill the systems a few times now.

 

[rubbersidedown]

Good write up @Mythos very well done.
Couple things to mention to the new mechanic.

• crud will be all over the inner lid,rubber and outer lid,clean with unused rag and new brake fluid. Don't use a shop rag that is contaminated with anything
• when "pumping up the pressure" do it with the rubber and inner lid on,it will splash,not necessary to put on outer lid and insert screws
• before your first pump and bleed,remove 95% of the old fluid (I use a large syringe without needle(new,only for brakes),or turkey baster(same,new),or the vacuum bleeder this saves time and doesn't subject the brake system to the ugly fluid in the master
• if the master is dirty at all,clean it out,a new toothbrush or similar works well,throw the brush away,new one each time.Keep your brake cleaning tools like a surgeon keeps his tools,no cross contamination with anything
• if not using a speed bleeder or vacuum use tape or mechanics wire,whatever, to keep the end of the tube from the master right to the bottom of your used fluid container.Once the tube is filled and some used fluid is in the container bottom it will help to stop air from entering the system,a smaller container will speed things up as opposed to a 1 gallon container as shown
• a better choice for a recovery container is clear (see any bubbles at a glance)
• I tap the lever/pedal aggressively before the first pump/hold/bleed action,removes tons of air
• soap and water is great for spills,but brake cleaner and new rags works awesome. If brake fluid has hit calipers and other surfaces brake cleaner will get it all removed better and faster than soap and water. I've used it on paint,if wiped off quickly,I've never damaged paint
• GoldenChild mentioned those 20 dollar bleeders,they work,they are essentially a mini one way valve,just note the directional arrow on them (arrow points towards recovery container,away from master)
• if you plan on any brake work in the future,just invest in a hand held vacuum tool. I have used the brand name MityVac for years and as Mythos mentioned it does double duty as vacuum leak tester,etc,works on any hydraulic system and is great for sukking that 95% of bad fluid prior to first pump/bleed
• don't be tempted to use any of your brake equipment for anything other than the DOT 3 or 4 fluid you are using,no sukking out old fuel or using it to clean wine/beer making equipment,no oil,etc...all that krap will eat brake parts IE seals,boots,etc
• if working on something that has been sitting a long time and you are installing new brake pads...the new pads will require that you push the calipers piston(s) back into their bore. Before doing this,clean/inspect the exposed piston(s) for dirt and pits/scoring. If you push a damaged piston back into the caliper it will ruin the inner seal.A damaged piston will have to be replaced and the caliper re-built or my preference,replaced.When squeezing 6 pot calipers back into the bore use the old brake pads to do it.If using large slip joint pliers or similar,something on the other side off the caliper to protect it from the jaws of the pliers. 2 sets of old pads could be used,or scrap metal with a large screwdriver or similar in between to force all the pistons back in at once. Doing 1 side at a time will just force other pistons out. If you are not concerned about opening the system,open a bleeder and force the pistons back,your fingers will do here. If you want to hurry the job along and skip alot of bleeding,force the pistons back (without opening a bleeder) but keep an' eye on your master,the level WILL rise and can spill over the top. Again,back to removing 95% of old fluid first. This will also speed your bleeding process helping to remove air...its called "reverse bleeding".
• using brake fluid from an open container is fine if you ask me,as long as it was re-sealed and stored properly after the last use. Shops do not buy little tiny bottles of fluid and throw out whats left over. They buy it buy the gallon,or bigger.
• Perfectly operating brakes are a must have on our Busa's...they go pretty fast.LOL.
• sound a n a l or OCD,welcome to my world...
  
• Rubb.

 

[Mythos]

Thanks @rubbersidedown. Good tips. Yeah, you're right about that old brake fluid. I guess once the seal is broken and outside air gets in, that air can have moisture in it but if a shop has a half full barrel, they don't throw it away.

I twist a piece of 1/4" plywood to pry brake pads apart while they're in the caliper. It works. Constant pressure seems to work as good as brute force. They usually don't have to be pried apart far to get the pads around the rotor again anyway.

I bought a Mityvac Silver and it works for sh!te. I'm the only one I ever heard complain about this tool but it won't suck hard enough to draw any fluid

I have heard fluid can squirt from the reservoir. I've never had it happen but placing the inner cover on there with the gasket is a wise precaution.

The only real crud I have found in my reservoirs is black sediment. I think that's rubber that has deteriorated from the gasket. I try to sop that up as best I can with a paper towel before it goes down the MC. That's a good suggestion to use a syringe or an eyedropper to remove most of the old fluid. I usually just pump it through to bleed until the old fluid is almost gone, then swab up the black sediment, fill the reservoir with fresh fluid and keep bleeding. Sometimes you just want to remove the old fluid in the reservoir. That should get rid of most of the fluid in the whole system or a lot of it at any rate. Then just fill the reservoir with fresh fluid. I try not to open those bleeders unless I really need to. They often seep a little after they've been opened and it can leave etched spots on plastic if you don't see them right away. 3M Scratch and Swirl Remover works well for buffing the lenses on gauges back but it's a hassle I'd rather avoid. I try to not open the bleeders or the reservoirs. The Kawasaki reservoirs always seep for a while and all you can do is wipe it up. They make those socks you can put over them to though. I have a couple Moto Mummy reservoir socks.

 

[rubbersidedown]

I wonder if your MityVac was just defective. Good company,they may replace it or gift certificate you.
Rubb.

 

[Mythos]

HA--yeah I think I might have just got a bad one but that was about 10 years ago. I might just buy a new one. The problem seems to be that the cup on the mightytVac has slits in the lid to lock onto the cup. Those slits let air in and there goes the vacuum. Maybe if I just RTV the slits before I use it next???

 

[13K24/7]

Great write-up - felt the need to append that for my Gen1 I pulled 3 ounces of clutch fluid in a complete fluid replacement before running clean fluid.