Rebuilding the Clutch Slave Unit for 1985 Yamaha FJ1100 (other
years should be simular).
By Gary Foreman
Tools: (N/A at this time)
Brake Fluid used: Bel-Ray DOT 5 (I use DOT 5 because I ruined a paint job once with DOT 3)
REVISED 12 MARCH, 2001: I have removed all DOT 5 from the bike. All the pistons in the slave cylinders on the clutch and brakes have a high tendency to corrode. I am now running DOT 4.
Remove the reservoir cover, and attach a bleeding hose. Pump as much brake fluid out as possible.
Removed Banjo bolt from slave unit.
Get a heavy-duty freezer zip-lock bag, and insert the end of the clutch line, and zip it tight. This will keep brake fluid from being slung all over the bike as you work.
Removed three bolts holding the unit on.
With the unit in hand, wrap it in a towel with the brake line hole exposed. Take an air compressor with a nozzle, and blow into the hole left open by the line being removed. (BE CAREFUL!) Mine shot out like a mortar round. Brake fluid will go everywhere if you don't have it wrapped!
With the piston removed, check the condition of the housing. If it is pitted bad you will have to replace it. Mine had some surface rust that I polished out with a Dremmel tool and a buffing wheel coated with Semichrome. It had a mirror finish when I was done.
Remove the old seals and clean the piston and spring. Coat the new seals with brake fluid before trying to put them on the piston, it will make them slide easy plus keep them from being cut by the sharp edges.
Assemble the unit. Don't forget the spring! To attach it to the piston, simply twist it on.
Once assembled, press the piston in and let it return. Is it smooth? It should be. Of not, check the mating surfaces again. More polishing may be needed.
Pour some brake fluid in the line hole. This will save you a lot of pumping and bleeding! Bolt the unit back on the bike, and attach the line.
Fill the reservoir on the master. START PUMPING. At times you feel you will never get it started. Pump about 10 hard pumps with the lever, and on the last one, hold it in and release the bleeder (you have a hose on it, right?). Keep an eye on the reservoir. If you let it run dry, you will be starting all over getting the air out again.
I have a vacuum bleeder, makes the job MUCH faster. Once it felt solid, I rode it for a few days, then bled once more just to be safe.