CLUTCH FLUID CHANGE

[SUPERCRUZ_imp]

We had some unseasonal and beautiful weather in northern VA this past weekend. I decided to get the bike out Sunday and ride. I noticed the clutch fluid appeared a bit discolored in the sight glass. It has been about 1.5 years since the bike was new so I decided to open the service manual and perform a clutch fluid change. Actually, very easy with the right tools.

Tools needed are one man bleeder (Mityvac), 10mm box wrench for bleeder screw for slave cylinder, hex wrench to remove left side plastic crank case cover, and small philips screw driver to remove clutch master cylinder reservoir cover.

Fluid - DOT 4 brake fluid. I used MOTUL 600 DOT4.

Start by setting the bike on a level surface and putting it on the center stand. Turn the handle bars slightly to the right or until the clutch master cylinder top is level.

Remove 10mm bolt holding holding the gear shift linkage on the left side of the bike. You will need to fully remove the bolt in order for the linkage to slide off the input shaft. Note the orientation of the shift linkage and the alignment dots on the linkage and end of the input shaft. Line these dots up when the linkage is reinstalled.

Remove the three hex head bolts securing the plastic crank case cover (left side of bike). Upon removal you should see the black clutch slave cylinder with the bleed nipple with rubber cover at the top. . Remove the rubber bleed nipple cover to allow access to the bleed nipple and bleeder screw.

Place a protective towel or sheet over the gas tank and front fender to prevent any errant cutch fluid from getting on painted surfaces. Clutch fluid is highly corrosive and will remove or stain paint if not removed immediately. Take extra precautions here. At the handlebars, remove the two philips screws securing the clutch master cylinder (left side) cover and rubber seal. Remove the cover and place in a safe place. Next, take your hand held bleeder and vacuum out all the fluid in the brake master. Do not pump the clutch handle as this may allow air to enter the system. Simply remove the contaminated fluid and refill the reservoir to the inner max level line with fresh DOT4 brake fluid.

Next, place a 10mm box wrench on the slave cylinder bleeder screw and attach your brake bleed tool hose to the slave cylinder bleed nipple. Using the bleed tool, draw a vacuum on the bleeder valve and then crack open the bleeder screw with the 10mm wrench. Watch the vacuum gauge drawn down as dirty fluid exits the bleed nipple. Tighten the bleed screw when the vacuum gauge approaches zero. Repeat this process until the fluid exiting the bleed nipple appears clear. It is okay if you see a few bubbles in the fluid that is exiting. I have learned over the years that you rarely get a solid stream of fluid. Most likely some air will come into the fluid exiting the bleed nipple from around the bleeder screw threads. This is okay as the bleeder is at the top of the slave cylinder so unlikely air is actually in the system. Be careful not to let the brake master empty completely of fluid or you will draw air into the system. I performed the bleed procedure and opened the bleed valve 4 -5 times under vacuum before the fluid was clear to my satisfaction. Tighten the bleeder valve screw for the last time, remove the hand held bleeder hose, and replace the rubber nipple cover.

Top the master cylinder up to the inner max level line and replace the cover and secure with two philips retaining screws.

Replace the crank case cover and shift linkage and you are done. You should have a firm and responsive clutch lever. Test ride the bike. Hope this helps everybody. :beerchug:

 

[the Ferret]

Great info. Moved to How To Section

Thanks SUPERCRUZ

 

[OldF7Guy_imp]

Curious how often this should be done?

 

[SUPERCRUZ_imp]

OldF7uy - I have a hydraulic clutch on my late model Corvette and it is critical to keep the fluid clean in those systems for proper clutch pedal operations Not sure if the CB is as sensitive to dirty fluid but as I said, my bike is about 1.5 years old and I could see small dirt particles floating in the fluid through the site glass. It was actually much dirtier than the brake fluid in the reservoir on the opposite side. I would say change the clutch fluid yearly but not later than 2 years max. Same goes for the brake system - 2 years max.

 

[the Ferret]

I imagine many bikes (and cars) go through their whole lives without having either the clutch or brake fluid changed. It is a good idea to change it however. Every 2 years is a good time frame...or anytime it changes from clear to " clean oil" colored (amber?).

 

[ClassicVW_imp]

I agree with your assumption, ferret. I bet those many of those 70s Hondas that have been sitting for 10 or more years don't get a fluid flush.

One word of caution that doesn't really apply here but could on other bikes or cars- the dark look of your brake or clutch or power steering fluid as seen through those clear reservoirs may be misleading. The resevoir's plastic material gets dark with age and the fluid inside could be much lighter. This was the case when I brought my car to one of those 10 minute oil change places. They are always looking to up-sell you to expensive flushes and the $40 replacement air filters, etc. They showed me my power steering resevoir and said the fluid needed to be flushed since it was so dark. I opened the fill cap and stuck in a corner of a piece of white paper and showed him how clean the actual fluid was and declined his offer of an added $60 fluid change. Made me wonder how many times that tactic works on customers.

 

[Django]

The Honda service manual, I got, says the same:
Clutch hydraulic and brake fluid exchange every 18.000 km or every 2 years, what ever comes first.

I'm not sure, if it's that critical for the clutch, but for the brakes keep in mind, the DOT 4 draws water over time. If the brake fluid contains water, it could vaporize when you braked very hard and long and the brakes were getting really hot, e.g. downhill. That could cause your brake is gone completely situations, like air in the brake hydraulic system.

 

[Cormanus]

Do you need the specialized bleeding tool to do this?

 

[SUPERCRUZ_imp]

Do you need the specialized bleeding tool to do this?

The Honda Service Manual outlines another clutch fluid replacement procedure without a bleeder tool. It involves attaching a clear tube to the bleed valve nipple. Run the other end of the clear tube to an empty container. An old plastic soda bottle with 3/8 " hole drilled in the cap works great. Pump the clutch handle ~10 times and then hold it in and open the bleeder screw 1/4 turn to allow fluid under pressure to bleed out. Close bleed screw and slowly allow the clutch handle to return to full extended position. Repeat the process until fluid coming from the bleed screw is clear. Note. This is more of a two man process and you must be careful not to allow the fluid in the clutch master reservoir to run empty during the bleed process. Do not allow the clutch handle to return to the open position with the bleed screw open or you may introduce air to the system. The process is much easier with a bleeder tool. I think my MItyvac hand held bleeder tool ran about $45.

 

[Django]

Additional to SUPERCRUZ's hint:

After attaching the clear tube to the bleed valve and removing the cover from the container, you can just open the bleed nipple srew a bit and pull the lever a little bit. This opens the pump in the handle far enough, that the fluid just starts to rinse out by gravity.

Keep filling after fresh fluid on top into the container, while it is draining. Avoid getting air into the system by refilling carefully!

If fresh fluid appears down in the clear tube, you can close the bleed valve, fluid is changed.

Be carefully and work clean. DOT 4 hydraulic liquid is aggressive to plastic and painting. Cover your fuel tank with an old t-shirt or something.

If you really need bleeding support, you can attach this to the clear tube to suck the fluid out:

 

[Cormanus]

Thank you, gentlemen.

 

[postoak_imp]

So the left side reservoir on the handlebar is for the clutch? What is the routing of the line down to the slave cylinder?

 

[Lord Popgun]

Comes out of the clutch actuator and goes under the tank on the left side. Right as it goes under the tank it transitions to a metal line and follows the top left frame rail follows it as it curves down by the plastic air box. Goes down and curves forward and transitions back to a hose and connects to the clutch slave. You can see that by removing the plastic that the gear shift shaft sticks out of.

You can't LOOK under the tank and see the line as there is a plastic heat shield that hides everything.

 

[Ulvetanna_imp]

So the left side reservoir on the handlebar is for the clutch? What is the routing of the line down to the slave cylinder?

If you are uncertain about those things, I'd recommend having your dealer do it. You don't want to mess up a clutch or brake fluid maintenance procedure. Dribbles of fluid mar the paint, air in the system degrades clutch or brake operation, sometimes seriously.

However, yes, the fluid reservoir on the left would naturally be for the clutch; the routing of the lines is not relevant as they do not need to be touched. The bleeder is accessible.

If getting the bike to a dealer to get this done seems expensive or time-consuming, I'd agree.

The interval specificed assumes a certain amount of wet-weather mileage and perhaps outdoor storage in humid locations.

If you, like me, never ride in the rain and live in a desert, you could likely extend this interval without any problem.

Looking at the inspection window doesn't really provide good information as the window itself can become discolored or accumulate a film on the inside that is deceptively troubling.

The level of the fluid is also important; it decreases as the brake pads wear. That is the only reason for the existence of the sight glass, to ensure sufficient quantity of the fluid. The regular changes/flushing are to ensure the quality of the fluid does not degrade.

 

[TCinNC_imp]

Performed this today, as well as front and rear brakes. I replaced all bleed screws with speed bleeders, made it very easy. Clutch fluid was far dirtier than either set of brakes.

 

[jimgl3_imp]

for clutch and/or brakes: does anyone here believe in replacing rubber reservoir gasket with new one every time?

 

[Lord Popgun]

I do. The service manager/head mech at my dealer said they always do it and have been bitten by leaks when they didn’t. So they do and I do. I flush the fluid every 2 years so the cost is cheap insurance as far as I’m concerned.

 

[jimgl3_imp]

yeah, this is my first hydraulic clutch, so I youtubed it to see how it's done and the guy said always put a new one, well I must admit, I have never replaced one. (brake type) never had a problem, but sounds like a good idea.

 

[Townie_imp]

Folks,

These rubber reservoir gaskets that you recommend replacing, do you know the part number?

On the fiche I see 2 items:
45518-MM5-006 (diaphragm plate)
45520-MM5-006 (diaphragm)

It's not exactly clear to me which one is the reservoir gasket. I think it's the first item above.

Can anyone help?

 

[Lord Popgun]

The part number on the bag I have is 45520-MM5-006

The head mech at my dealer says to always replace them too. So I do.