The CB1100 Community Forum

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.

Great info. Moved to How To Section

Thanks SUPERCRUZ

Curious how often this should be done?

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.

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?).

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.

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.

Do you need the specialized bleeding tool to do this?

(01-01-2015, 06:29 AM)Cormanus_imp Wrote: [ -> ]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.

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: