How to Bleed Motorbike Brakes

Motorcycles once featured only mechanical drum brakes, just as all automobiles did in their early years. As motorcycles became larger, faster, and more widely used, the brakes required a serious overhaul, with Honda offering upon an aftermarket set of disc brakes. Honda first successfully attached these brakes to its CB450 and revealed the CB750 to the world with the first standard disc brakes at the 1966 Tokyo Motor Show. With these disc brakes which are standard on the front of nearly all present-day motorcycles comes hydraulic fluid and the need to periodically bleed the air out of the braking system.

Instructions

Bleeding the Front Brakes

1

Open the brake master cylinder reservoir. This process varies, depending on the type of motorcycle, but there are two common ways. The most common is to remove the screws on the rectangular cover on top of the master cylinder with a Phillips screwdriver and pull the cover off the master cylinder. The second way is to unscrew the cap from the reservoir. Refer to your owners manual if your motorcycle does not have either feature.

2

Fill the master cylinder reservoir with the brake fluid prescribed for your motorcycle by the owner's manual typically DOT 3. Keep the master cylinder from running out of fluid throughout the entire bleeding process.

3

Find the bleeder valve on the brake master cylinder the -inch metal valve if applicable. Remove the rubber cap from the bleeder valve. Not every motorcycle has a bleeder valve on the master cylinder; proceed to Step 9 if your motorcycle does not have a master cylinder bleeder valve.

4

Press a -inch-diameter clear vinyl hose to the end of the bleeder valve. Set the free end of the hose into a clean and clear container. Fill the container with the type of brake fluid prescribed in your motorcycles owners manual until the fluid submerges the end of the hose.

5

Pull and release the front brake lever repeatedly until you feel the lever get hard. Hold the lever inward, and turn the bleeder valve about a quarter-turn counterclockwise with a combination wrench to open it. Watch the fluid as it flows through the hose and look for bubbles bubbles mean it requires more bleeding.

6

Tighten the bleeder valve by turning it clockwise with a combination wrench, then release the brake lever.

7

Repeat Steps 5 and 6 until little or no bubbles appear in the fluid flowing through the hose.

8

Pinch the vinyl hose to prevent fluid from flowing out, and pull it from the bleeder valve.

9

Look on the top of the brake caliper to locate its bleeder valve. Pull the rubber cap from the bleeder valve. Press the -inch vinyl hose onto the bleeder valve and repeat Steps 5 through 7 to bleed the front caliper.

10

Repeat Steps 8 and 9 on the caliper on the other side of the front wheel, if applicable.

11

Pull the front brake lever and check that it feels firm and not soft or spongy. If it feels soft or spongy, repeat Steps 1 through 10.

12

Position the small container under the bleeder valve, and pull the hose off the bleeder valve.

13

Press the rubber caps back onto each of the bleeder valves.

Bleeding the Rear Brakes

14

Locate the rear brake master cylinder reservoir. The exact location varies on every motorcycle, but most manufacturers install it on the rearmost part of the frame just in front of the swing arm. If your motorcycle does not have rear disc brakes, it will not have a rear master cylinder reservoir, nor will the rear brakes need bleeding.

15

Pull the cap from the rear master cylinder reservoir. Add the brake fluid prescribed for your motorcycle typically DOT 3 to the master cylinder reservoir until it reaches the Max line. Allowing the master cylinder reservoir to run out of fluid during this process negates all of the bleeding performed, so keep the master cylinder reservoir filled with fluid throughout the bleeding process.

16

Find the bleeder valve the -inch metal valve on the rear caliper. Pull the rubber cap off the bleeder valve.

17

Press a -inch-diameter clear vinyl hose onto the end of the bleeder valve. Set the other end of the hose in a clean and clear container.

18

Fill the clean and clear container with the brake fluid until the fluid submerges the clear hose.

19

Instruct an assistant to press and release the rear brake pedal until it feels firm typically five to 10 strokes then hold downward pressure on the pedal. Open the bleeder valve by turning it a quarter-turn counter clockwise with a combination wrench, and watch for bubbles in the fluid flowing through the hose.

20

Tighten the bleeder valve to close it, and instruct your assistant to release the rear brake pedal.

21

Repeat Steps 5 and 6 until no bubbles appear in the fluid flowing through the clear hose.

22

Pull the hose off the bleeder valve. Press the rubber cap back onto the bleeder valve.