A motorcycle's brakes are an important part of its design. Improperly adjusted brakes can place a motorcyclist in a dangerous predicament without the ability to safely and effectively slow down. Older-style drum brakes, which use mechanical controls, often require minor adjustments to operate at peak efficiency. Conversely, modern hydraulic brakes are susceptible to air bubbles and condensation build-up within the brake circuit. In most cases, basic adjustments can be performed on both systems using basic hand tools.
Adjust the front brake drum. Twist the locknuts on the drum's cable adjuster and brake rod arm counterclockwise with a wrench to loosen the adjusters. Using a wrench, twist the cable adjuster counterclockwise to tighten the cable tension or clockwise to loosen the tension. Spin the front wheel slightly to test the engagement of the front brake. Adjust the cable until the front brake just begins to slow the front wheel as it spins. Adjust the brake rod arm using a wrench, twisting it counterclockwise to tighten the arm and clockwise to loosen it. Stop when the front brake can effectively stop the front wheel when the brake lever is pulled in. Tighten both locknuts with a wrench.
Adjust the cable tension at the front brake lever perch. Twist the large round locknut on the cable adjuster counterclockwise to loosen it. Twist the cable adjuster counterclockwise to tighten the cable tension, loosen the cable by twisting the cable adjuster clockwise. Adjust the cable tension until the brake lever has 1/8-inch of free play before engaging the brake. Twist the locknut clockwise until it is seated firmly against the brake lever perch.
Adjust the rear brake, using a wrench to loosen the brake rod's locknut. Twist the wing nut on the end of the brake rod to adjust the brake engagement point. To engage the rear brake earlier, twist the wing nut clockwise. Twist the wing nut counterclockwise to require more effort to engage the rear brake. Tighten the brake rod's locknut with a wrench once you are satisfied.
Adjust the front brake lever using the rotating adjuster on the lever's pivot. Push the brake lever forward slightly, twist the adjuster to the desired setting and release the lever. Adjust the rear brake pedal, using a wrench to loosen the locknut on the pedal's threaded adjustment rod. Twist the adjustment rod clockwise to engage the brake earlier and counterclockwise to engage the brake later.
Reset the brake caliper's pistons. Remove the caliper from the motorcycle. Insert a large flat screwdriver into the caliper, between the brake pads, and push the pistons back into the caliper housing. Reinstall the caliper onto the motorcycle and pump the brake pedal or lever repeatedly to rebuild hydraulic pressure and close the piston around the brake rotor. Stop when the lever or pedal requires a firm pull to engage the brake.
Bleed the brake circuit. Attach a length of clear plastic hose to the brake caliper's bleed valve and open the brake master cylinder's fluid reservoir. Place the open end of the hose into a jar or container. Using a wrench, turn the bleed valve clockwise one-quarter turn to open the valve. Pull in the brake lever and hold it in place to force a small amount of brake fluid into the plastic hose. Close the bleed valve, turning it one-quarter turn clockwise with a wrench. Release the brake lever. Refill the master cylinder's reservoir with fresh brake fluid as needed. Repeat as necessary until the brake fluid in the hose is clear and free of bubbles and debris.
Don't allow the master cylinder reservoir to drain completely. This will allow air into the brake circuit, requiring you to start the process over again.
Tips and warnings
- Don't allow the master cylinder reservoir to drain completely. This will allow air into the brake circuit, requiring you to start the process over again.