I thought this might be useful to some…
On the hydrolic clutch circuit, the master cylinder is located at the clutch lever and the slave cylinder is located on the transmission housing. As hose runs between the master to the slave cylinders. A bleed hose is attached to the slave cylinder and a “ball bearing type” check valve is attached to the end of the bleed hose.
This picture shows the end of the bleed hose as it is zip-tied to the frame.
This picture shows the capped end of the bleed hose and the protective sleeve.
This picture shows the check valve fitting on the end of the bleed hose.
This picture shows the cap removed and the check valve inside the fitting.
This picture shows the “bleeder” fitting (about $9) needed to attach to the end of the check valve. The bleeder fitting pushes open the check valve and allows you to easily flush the circuit.
This picture shows the two fittings assembled. Finger tight is all it takes.
This Mityvac system (about $75) makes it much easier to flush clutch and brake circuits.
This picture shows the dirty DOT4 fluid in the reservoir. Most of this was removed before I added fresh fluid.
This picture shows the assembled vacuum system. The inline needle valve is helpful.
This picture shows clean fluid in the reservoir. However, notice the grime on the walls of the reservoir. I did not see this until I looked at the picture. Looks like I have a little more work to do.
There… that’s better…
I suggest that you flush the circuit until clean fluid is continuously coming out and then remove the bleeder fitting from the check valve. Then work the clutch lever several times to pump the slave cylinder. Then flush the circuit again. I did this three times and by then end all of the fluid coming out looked clean.
My bike is an 04 R1150GS with 26k miles. I recently took a long ride (8094 miles) from Idaho Falls, ID, to Deadhorse, AK, and the only problem I had with the bike during the trip was the clutch circuit. It had never been flushed and this caught up with me on my trip when, along the Cassiar Highway, it decided to stop working. I flushed the circuit on the road by holding the check valve open with a screw driver and this brought the clutch back and I was able to finish my ride with only a few hours interruption. Today I properly flushed the circuit and now it feels 100% again.
Here is a schematic of the clutch circuit for reference. It does not appear that there is much to “rebuild”. If the master or slave cylinder goes out, you have to replace the units. The master cylinder or “clutch handlebar fitting” (#1) is about $385 and the slave cylinder or “output cylinder clutch” (#6) is about $127.
STOP THE PRESSES!!! Updated on August 8, 2009.
Thanks to the good advice from this site, I discovered the real problem.
This picture shows the slave cylinder being removed.
This picture shows the condition of the slave cylinder.
This picture shows the condition of the location occupied by the slave cylinder.
The bottom line is this, if the DOT4 fluid in the clutch system turns muddy, then the slave cylinder is shot.
I just order a new slave cylinder and gaskets. To access the slave cylinder I removed the muffler, rear tire, and rear shock.
Updated on August 17, 2009.
I installed the new slave cylinder over the weekend and this is what happened. When I finished the installation I filled and flushed the clutch system (with the new and dry slave cylinder) with DOT4 fluid using the Mityvac. However, at one point during the procedure the DOT4 fluid would no longer flow out of the check valve and into the Mityvac. I would pump the clutch lever but no more fluid would drain out through the check valve, despite the vacuum. I buttoned everything up and took the bike for a ride. I was disappointed because the clutch lever did not feel much better with the new slave cylinder than it did with the old slave cylinder. However, when I got back home I decided to flush the system again and this second time I had none of the same problems as the first time. On my next ride the clutch lever felt 100% again. It seems that I did not get all of the air out of the clutch system on my first flush after installing the new slave cylinder.