Bleeding the Front Brake on a 1979 Honda CX500

Shop parts for a 1979 Honda CX500 Motorcycle.

The 1979 Honda CX500 uses a hydraulic front disc brake and a mechanical rear drum. Only the front system contains brake fluid, a master cylinder, a hose, and a caliper, so it is the system you bleed. The rear drum is adjusted, not bled. This CX500 predates ABS and linked brakes, so there is no ABS unit or combined-brake sequence to account for. The job below flushes old fluid from the front circuit and removes air.

What the CX500 Layout Means for Bleeding

Because the rear brake is a drum, there is no rear bleeder valve or rear master cylinder to service. Leave the rear drum alone except for normal adjustment. All bleeding work happens at the front master cylinder, line, and caliper. The goal is to push fresh fluid from the reservoir through the line and caliper while carrying air and old fluid out through the caliper bleeder. Work slowly, keep the reservoir from running dry, and treat every drop of brake fluid as something that can damage paint and plastic.

When to Bleed and Why It Matters

Bleed the front brake if the lever feels spongy, pulls closer to the grip than it used to, slowly sinks under steady pressure, or if reservoir fluid looks dark, cloudy, or contaminated. A bleed is also required after new lines, caliper service, master-cylinder work, or a fluid change. Even without symptoms, brake fluid absorbs moisture over time; that lowers its boiling point and can contribute to fade under hard braking, so many riders refresh fluid on a schedule. If you are replacing pads or lines, plan the bleed as the final step.

Tools and Supplies to Have Ready

  • Fresh brake fluid of the type marked on the reservoir cap, from a sealed container.
  • A box-end wrench that fits the front caliper bleeder.
  • Clear tubing that fits snugly over the bleeder.
  • A catch bottle.
  • Rags or shop towels, plus a syringe or turkey baster.
  • The correct driver for the reservoir cap screws.
  • Optional: a one-way check-valve or vacuum bleeder for one-person work.

A box-end wrench grips the bleeder better than an open-end wrench and reduces rounding. Keep fluid capped when not pouring, and do not reuse fluid that has been open.

Prepare the Bike and Protect the Finish

Support the CX500 upright on a stand so it cannot tip while you work the lever. Turn the handlebars until the front reservoir sits level; a tilted reservoir makes the fluid level hard to judge and can spill as soon as the cap comes off. Cover painted bodywork, instruments, and plastic near the reservoir with rags. Most brake fluids damage paint and plastic on contact, so wipe spills immediately and rinse with water if fluid reaches a painted or plastic surface. Position the catch bottle before opening the bleeder, and keep the cap and diaphragm clean.

Step-by-Step: Flushing and Bleeding the Front Brake

  1. Clean the reservoir top. Remove the cap and diaphragm; draw most old fluid out with the syringe or baster. Do not pump the lever with the reservoir empty, and never let it run dry.
  2. Refill with fresh fluid of the type marked on the cap, leaving the air space indicated by the markings. Keep the cap nearby; you will top off repeatedly.
  3. Push the clear tubing onto the front caliper bleeder and route it into the catch bottle. The tubing must fit snugly so air cannot enter around it. Position the bottle where you can see the fluid.
  4. Squeeze the lever several times to build pressure, then hold it firmly against the grip. Keep steady pressure while opening the bleeder.
  5. Open the bleeder about a quarter turn. Fluid and air move down the tubing. Watch the reservoir; if it gets low, close the bleeder and refill before continuing.
  6. Close the bleeder before releasing the lever. Releasing with the bleeder open can draw air back in. Then release, wait, and pump again.
  7. Repeat the squeeze-hold-open-close-release cycle. Keep topping off so the reservoir never drops low enough to pull air into the master cylinder. Continue until fluid is fresh, clean, and bubble-free.
  8. If your particular CX500 has a second front caliper, bleed it as a separate point after the first, working from the caliper farthest from the master cylinder toward the closer one. Top off between calipers.
  9. When fluid runs clear and bubble-free, close the bleeder snugly with the box-end wrench. Tighten enough to seal, but do not overtighten or you can damage the caliper or bleeder seat.

Finishing Up and Testing Before You Ride

Fill the reservoir to the correct level, reinstall the diaphragm and cap, and wipe away spilled fluid. Check the bleeder and banjo fittings at the master cylinder and caliper for wetness. Pump the lever; it should feel firm and consistent, not spongy, and should not slowly sink under steady pressure. Spin the front wheel to confirm no drag. Test at low speed in a safe area before riding normally, then check again after a short ride.

Troubleshooting and When to Take It to a Shop

If the lever will not firm up after several attempts, firms only after pumping, or bubbles keep appearing, stop and look for a cause. Possibilities include air drawn in at the bleeder threads, a reservoir that ran low, a loose fitting, or a worn master-cylinder cup. Because this CX500 has no ABS or linked-brake hardware, you do not have to worry about air trapped in an ABS module or combined-brake sequence. If fluid leaks from the master cylinder or caliper, or the lever still will not hold firm pressure after careful bleeding, have the bike inspected by a shop. A persistent soft lever is not something to ride around.

Related Shopping Categories

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Shop Brake Tools for a 1979 Honda CX500 Motorcycle.

Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.