Air bleeding from brake fluid circuit

Air trapped in the brake fluid circuit acts like a cushion to absorb a large proportion of the pressure developed by the master cylinder and thus interferes with the full braking performance of the brake caliper. The presence of air is indicated by “sponginess” of the brake lever and also by lack of braking force. Considering the danger to which such trapped air exposes the machine and rider, it is essential that after remounting the brake and restoring the brake system to the normal condition, the brake fluid circuit be purged of air in the following manner:

handle brake fluid with care: the fluid reacts chemically with paint, plastic, rubber materials, etc.

if air is trapped in the master cylinder, bleed air from the master cylinder first in the same manner as follows. Refer to “front brake master cylinder assembly removal and installation” .

1. 1
   Remove the reservoir cap and diaphragm.
2. 2
   Fill the reservoir with brake fluid to the upper line of the reservoir. Place the reservoir cap to prevent dirt from entering.

   

1. 1
   Attach a hose to the air bleeder valve, and insert the free end of the hose into a receptacle.
2. 2
   Squeeze and release the brake lever several times in rapid succession and squeeze the lever fully without releasing it.

   

1. 1
   Loosen the air bleeder valve by turning it a quarter of a turn so that the brake fluid runs into the receptacle, this will remove the tension of the brake lever causing it to touch the handlebar grip.
2. 2
   Close the air bleeder valve, pump and squeeze the lever, and open the valve.
3. 3
   Repeat this process until the fluid flowing into the receptacle no longer contains air bubbles.

Make sure that there is always some fluid visible in the reservoir.

8. Close the air bleeder valve and disconnect the hose.

9. Fill the reservoir with brake fluid to the upper line of the reservoir.

10. Install the diaphragm and reservoir cap.

1. 1
   Remove the right side frame cover. Refer to “exterior parts removal and installation” in section 9d .
2. 2
   Remove the rear brake fluid reservoir mounting bolt (1).

   

1. 1
   Remove the reservoir cap and diaphragm.
2. 2
   Fill the reservoir with brake fluid to the upper line of the reservoir. Place the reservoir cap to prevent dirt from entering.

   

the difference of bleeding operation from the front brake is that the rear master cylinder is actuated by a pedal.

5. Fill the reservoir with brake fluid to the upper line of the reservoir.

1. 1
   Install the diaphragm and reservoir cap.
2. 2
   Install the removed parts.