How to Bleed Harley Brake Lines

by Aryeh Raphael
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When air is trapped in your Harley brake lines, your braking power is diminshed if not fully lost. When this happens, your brake levers will feel spongy, making it hard to maneuver the motorcycle. Fixing the problem requires bleeding your Harley brake lines in order to remove the trapped air. The entire process may be time-consuming, but anyone with a few tools and a little familiarity with the motorcycle parts can do it.

Step 1

Find the bleed valve of your Harley on its rear brake caliper. Remove the caliper's rubber cap and slip one end of your clear plastic tubing over the nipple of your bleed valve. Route the tube's opposite end to your jar.

Step 2

Remove the reservoir cover of your rear brake master cylinder. Use your 4mm socket to get remove the pair of bolts used to secure your master cylinder's cover. Remove the reservoir cover and pull your rubber diaphragm out of your master cylinder if it doesn't come up with the reservoir. Get your fresh DOT 4 brake fluid and top off your reservoir with it.

Step 3

Use your 9mm wrench to open the bleed valve by turning it clockwise about ¼ turn. Push your rear-brake pedal down in order to hold it in position. Brake fluid should rush into your plastic tubing. Be looking for air bubbles to appear in the tubing. Before you release the brake pedal, close the bleed valve by turning it counterclockwise. Release your brake pedal.

Step 4

Open your bleed valve again and press down your Harley's rear brake pedal again in order to force more of your brake fluid into your plastic tubing. Close your valve and release your pedal. Repeat, if necessary, while keeping your reservoir for the brake master cylinder filled with the DOT 4 brake fluid. Do not stop bleeding the Harley's brake until the tubing becomes free of bubbles.

Step 5

Turn your bleed valve counterclockwise in order to close it, and pull out your plastic tubing. Press your rubber cap over the nipple of your bleed valve. Pump your Harley's brake pedal slowly in order to remove any air bubbles that may be trapped within the master cylinder. Insert the rubber diaphragm into the master cylinder and replace the reservoir cover. Secure the cover by tightening the bolts with your 4-millimeter socket.

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