How To Bleed 2020 Honda Super Cub ABS Motorcycle Brakes

Bleeding the Front Brake on a 2020 Honda Super Cub ABS

What the 2020 Super Cub ABS brake layout means for this job

The 2020 Honda Super Cub ABS uses a hydraulic disc brake at the front and a mechanical drum brake at the rear. That distinction matters before you pick up a wrench: the front system is the one that contains brake fluid, a master cylinder, a hose, and a caliper, so it is the circuit you bleed. The rear drum is operated by linkage and does not use brake fluid at all; it is adjusted, not bled. Because this MMY is an ABS model, the front hydraulic circuit also includes ABS hardware. For routine fluid refresh and air removal at the caliper, a normal bleed through the caliper bleeder is generally the right approach. If the reservoir has run dry, or if the ABS unit or its lines have been disconnected, air may be trapped inside the ABS unit itself. That is not a home-garage bleed on this bike; it calls for a dealer-level procedure or diagnostic tool.

When bleeding is needed and why fresh fluid matters

Bleed the front brake when the lever feels spongy, pulls closer to the grip than it used to, or slowly sinks under steady pressure. Dark or cloudy fluid in the reservoir is another sign. You also need to bleed after any work that opened the hydraulic system, such as replacing the brake hose, servicing the caliper, or repairing the master cylinder. Even without symptoms, brake fluid absorbs moisture over time. Moisture lowers the fluid’s boiling point, and under hard or repeated braking that can lead to fade. Many riders refresh the fluid on a regular schedule as preventive maintenance. Use only fresh brake fluid of the type marked on the master cylinder reservoir cap, and use it from a sealed container.

Tools and supplies to gather first

• Fresh brake fluid of the type printed on the reservoir cap, from a sealed container
• A box-end wrench that fits the caliper bleeder valve
• Clear tubing that fits snugly over the bleeder valve
• A small catch bottle for old fluid
• Rags or shop towels, plus a syringe or turkey baster for removing old fluid from the reservoir
• The correct driver for the reservoir cap screws
• Optional: a one-way check-valve bleeder or vacuum bleeder, which can make a one-person bleed easier

Work with the bike supported securely upright on a stand. Turn the handlebars so the front reservoir sits level before you open it. Cover painted surfaces, plastic panels, and the instrument area with rags. Most brake fluid damages paint and plastic on contact, so wipe up any spill immediately and rinse the area with water.

Opening the reservoir and starting with fresh fluid

Clean the top of the reservoir before removing the cap so dirt does not fall into the system. Take off the cap and diaphragm, then use the syringe or turkey baster to remove most of the old fluid from the reservoir. Do not let the reservoir run dry at any point in the job. Refill with fresh fluid from the sealed container, leaving enough room to reinstall the diaphragm later. Keep the cap and diaphragm clean and set them aside where they will not pick up grit.

Bleeding the front hydraulic brake step by step

1. Fit the clear tubing over the caliper bleeder valve and route the other end into the catch bottle. Keep the bottle lower than the caliper so fluid and air flow away from the bleeder.
2. Make sure the reservoir is topped up with fresh fluid. Squeeze the front brake lever slowly and hold it against the grip.
3. With the lever held, open the bleeder valve about a quarter turn. Fluid and any trapped air will move through the clear tube. Watch the tube, not the reservoir, while the bleeder is open.
4. Close the bleeder valve before you release the lever. Releasing the lever with the bleeder open can draw air back into the caliper.
5. Release the lever slowly, then check the reservoir level and top it off with fresh fluid. Repeat the squeeze, hold, open, close, and release sequence.
6. Continue until the fluid coming through the clear tube is clean, fresh-looking, and free of bubbles. Do not stop just because the lever feels better; confirm the fluid condition at the tube.
7. Keep topping off the reservoir throughout the process. If the level drops low enough to uncover the master cylinder port, air will be drawn into the system and you will have to bleed again.
8. When the fluid is clean and bubble-free, close the bleeder snugly without overtightening it. A box-end wrench gives you good control, but stop before you crush or distort the bleeder.

If you are ever bleeding a circuit with more than one caliper, the general practice is to start with the caliper farthest from the master cylinder. On the 2020 Super Cub, the front hydraulic brake is handled as its own circuit, and the rear drum is not part of the bleed.

Finishing the job and checking for leaks

Fill the reservoir to the correct level marking, then reinstall the diaphragm and cap. Wipe any spilled fluid from the caliper, hose, reservoir, and surrounding surfaces, and rinse with water if fluid touched paint or plastic. Check the bleeder valve and the banjo fittings at the master cylinder and caliper for weeping or wetness. A dry paper towel wiped around each fitting will show a leak quickly. If you see fluid, stop and correct it before riding.

Testing the brake before normal riding

The front lever should feel firm and consistent, not spongy, and it should not slowly sink while you hold steady pressure. Spin the front wheel to confirm the brake is not dragging. Test the brake at low speed in a safe area, such as an empty parking lot, before riding normally. If the lever changes feel after the test, or if it firms up only after several pumps, there is still air in the system.

Troubleshooting and when to send the bike to a shop

If the lever will not firm up after several bleeding attempts, if bubbles keep appearing, or if fluid is leaking from the master cylinder or caliper, stop and diagnose the problem rather than continuing to pump fluid through. Persistent air often points to a fitting that is not sealing, a hose that is drawing air, or a master cylinder issue. Because this is an ABS model, any situation where air may have entered the ABS unit — especially a reservoir that ran dry or ABS hardware that was disconnected — should go to a shop with the appropriate diagnostic equipment. A lever that never becomes firm is not a brake you should test on the road.

Related Shopping Categories

Shop Brake Fluid for a 2020 Honda Super Cub ABS Motorcycle.

Shop Brake Lines for a 2020 Honda Super Cub ABS Motorcycle.

Shop Brake Pads for a 2020 Honda Super Cub ABS Motorcycle.

Shop Stands for a 2020 Honda Super Cub ABS Motorcycle.

Shop Brake Tools for a 2020 Honda Super Cub ABS 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.