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Motorcycle Maintenance: How to Service Your Master Brake Cylinder


(Image Source: Flickr)

While you may pay plenty of attention to the brake pads and callipers on your motorbike, it is easy to forget about the master brake cylinder. The master brake cylinder contains the brake fluid which creates the energy needed to slow and stop your bike. The cylinder contains a rubber seal which needs to be periodically inspected and replaced. Below is a guide on how to perform this task.

Remove the master cylinder

Removing the master cylinder is a relatively straightforward affair. Put on a pair of work gloves to protect your hands, and then use a spanner to loosen the bolt which holds the fluid line hose. As you do this, you should keep your eye open for any drops of brake fluid which leak out. If brake fluid comes into contact with the bodywork of your bike, it can cause damage to the paint, so you should wash it off using water as soon as possible. Next, you should loosen the bolts that hold the brake lever in place. Disconnect the electrical brake light wiring and lift the brake cylinder away from the machine.

Drain and clean the cylinder

Once you have removed the cylinder, you should remove the reservoir lid and pour out the brake fluid it contains. You can then spray some brake cleaning product into the reservoir to remove any residue which has built up inside.

Prepare your work area

Carrying out maintenance on the master cylinder is a job which should be done on a clean workbench or another surface in your home, as this will minimise the risk that any dirt or debris will become trapped in the system. If you do not have a workbench, you should lay out sheets of newspaper on a kitchen or dining room table. Replacement master cylinder seals can be purchased at any auto repair shop or motorcycle dealership.

Replace the seal and service the piston

You should find that there is a small rubber seal on the piston end where the lever connects to it. You can pop this off using a small screwdriver. Beneath you will see a circlip which holds the piston in place against the pressure of the spring. Remove the circlip using a pair of pliers and then lift the moving parts out of the cylinder. You can now check inside the bore of the cylinder to make sure it is clean. Giving it a little blast of brake cleaner can help to remove any dirt and debris. Lubricate the piston and reinsert it into the cylinder bore. Hook the circlip into place and then place a new rubber seal over the top of it. Next, reattach the cylinder and hook up the fluid and brake light lines. Finally, you will need to refill the reservoir with fresh brake fluid and then bleed any air which is trapped in the system.

So, what are you waiting for? Check out the master cylinder on your bike today!