Reverse bleeding the clutch


On a bike the clutch is a pretty useful thing to have working. I have had a couple of incidents in the past with non working clutch, in southern Brazil and in Holland, and it is a pain especially when starting the bike. However, the clutch is not as critical as in a car and especially at speed you can change gear without using the clutch. I heard MX riders prefer to do it instead of letting go of critical fingers on the handlebar. However, given I have time before departure and the fact I haven't even change the clutch fluid once since I bought the bike I reckon it was about time anyway to give it some love.

First of all you need some tools. A large syringe with a hose and some new fresh hydraulic fluid. I found some of the Motorex hydraulic fluid in the bike shop nearby. A second syringe is handy as well to empty the master cylinder with and this one needs no hose.

Key tools is a 8mm wrench for the bleeder valve on the slave cylinder and a 5mm hex key to loosen the master cylinder with. You also need a screwdriver, not shown, for the master cylinder. 

Start by loosening the nut on the master cylinder to get the cylinder even with the ground.

Tie a rag around the opened cylinder and clean it out with a syringe and a rag. Mine was quite dirty inside so felt like a good thing that I did decide to service it.

Locate the bleeding nipple on the slave cylinder and remove the cap.

You find it where the orange circle is.

I decided to first flush some fresh fluid thru so attached a hose and a bucket. I reckon this is not needed though.

Attach the syringe with fluid filled hose to the bleeder valve. Try to get as little air into the hose as possible. However, as long as the air bubbles stays on top of the hose and not going into the nipple it should be fine.

Put the wrench in place on the bleeder nipple.

Now comes the key part: Loosen the nipple about 1/2 a turn, hold the hose in place with one hand and force a few ml of fresh fluid into the system from below i.e. in the reverse direction and close the bleeder nut. This will increase the fluid in the master cylinder so use the second syringe to empty it out.

Repeat the procedure until you are sure you flushed the entire system without dripping too much fluid on the ground. When it was all clean fluid coming out in the master cylinder and I used up most of the fluid in the syringe I deemed the job to be done.

Check the master cylinder and let 4mm of gap remain from the top of the fluid to the top of the cylinder. Put the lid back and fasten with the two screws. Wipe any excess fluid off with the rag and position the clutch back where it is comfortable to use.


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