How To Bleed 2020 Honda Grom ABS Motorcycle Brakes

Bleeding the Brakes on a 2020 Honda Grom ABS

The 2020 Honda Grom ABS uses a hydraulic disc brake at each end of the bike, and both systems are equipped with anti-lock braking. That means there are two separate hydraulic circuits to think about — a front circuit fed by the lever-mounted master cylinder and a rear circuit fed by the pedal master cylinder — and each one has its own reservoir, its own line, and its own caliper bleeder. Neither circuit is linked to the other, so you can service them one at a time and in whichever order you prefer. This guide walks you through refreshing the fluid and purging air from both circuits in your own garage, using ordinary hand tools and a little patience.

When a Grom ABS Needs Its Brakes Bled

The most obvious trigger is feel. If the front lever has gone soft or spongy, or if it now travels noticeably closer to the grip before the brakes bite, air has likely found its way into the circuit. The same goes for a rear pedal that feels vague or requires a longer stroke than it used to. A lever or pedal that slowly sinks toward the end of its travel while you hold steady pressure is another classic sign of a hydraulic problem.

Visual clues matter too. Pop the reservoir cap and look at the fluid: fresh brake fluid is clear and light, while fluid that has been in service for a few years turns dark, cloudy, or tea-colored. Brake fluid is hygroscopic, meaning it absorbs moisture from the air over time, and that moisture lowers the fluid's boiling point. Under hard or repeated braking, fluid with a high moisture content can boil and create gas in the lines, which shows up as fade or a long lever. Many riders simply refresh the fluid on a regular interval rather than waiting for symptoms. You should also bleed after any work that opened the hydraulic system — new brake lines, a caliper rebuild, or master cylinder service.

Tools and Supplies to Gather First

• Fresh brake fluid of the type printed on the master cylinder reservoir cap, from a sealed container
• A box-end wrench that fits the bleeder valve on each caliper
• Clear tubing sized to fit snugly over the bleeder nipple
• A small catch bottle for the old fluid
• Rags or shop towels, plus a syringe or turkey baster for pulling old fluid out of the reservoir
• The correct driver for the reservoir cap screws

A one-way check-valve bleeder or a vacuum bleeder is not required, but either one makes the job much easier to complete solo, since you no longer have to coordinate the lever and the bleeder valve at the same time.

Setting Up Safely

Get the Grom supported securely and upright on a stand so it cannot tip while you are working. For the front circuit, turn the handlebars until the reservoir on the lever assembly sits level; a reservoir that is tilted will spill as soon as you open it. Before you touch anything, drape rags over the painted bodywork, the plastics, the instrument cluster, and anything else below the reservoir. Brake fluid attacks paint and many plastics on contact, so any drip should be wiped up immediately, and the area rinsed with water if a spill does occur.

Bleeding the Front Brake

1. Remove the reservoir cap and diaphragm, then use the syringe or baster to draw most of the old fluid out of the reservoir. Leave a little in the bottom so you do not push air into the master cylinder.
2. Refill the reservoir with fresh fluid from your sealed container.
3. Slip the clear tubing over the front caliper bleeder and route the other end into the catch bottle, with the bottle positioned so you can see the fluid coming through the tube.
4. Fit the box-end wrench onto the bleeder. Squeeze the front lever and hold it firm.
5. Open the bleeder about a quarter turn. Fluid and any trapped air will push out through the tube. Watch the reservoir level as you do this.
6. Close the bleeder before you release the lever. Releasing with the bleeder open draws air back into the caliper.
7. Repeat the squeeze–hold–open–close–release cycle, topping off the reservoir between cycles so it never runs low enough to pull air in. Continue until the fluid arriving in the tube is clean and free of bubbles.
8. If your bike has two front calipers, bleed each one in turn, starting with the caliper farthest from the master cylinder.

Bleeding the Rear Brake

The rear circuit on the Grom ABS works the same way, just with a pedal instead of a lever. Open the rear reservoir, remove most of the old fluid, and top it up with fresh fluid. Attach the tubing to the rear caliper bleeder and run it to the catch bottle. Press and hold the pedal, crack the bleeder a quarter turn, let the fluid and air escape, then close the bleeder before releasing the pedal. Keep the reservoir topped off throughout and repeat until the fluid runs clean and bubble-free.

Finishing and Checking Your Work

When both circuits are done, tighten each bleeder snugly with the box-end wrench — firm enough to seal, but not so tight that you risk damaging the caliper threads. Fill each reservoir to the correct level marking, reinstall the diaphragm and cap, and wipe away any fluid residue. Inspect the bleeder valves and the banjo fittings at the calipers and master cylinders for weeping or dampness; a leak here means something is not seated properly.

Before you ride, check the feel. The lever and pedal should be firm and consistent, and neither should creep toward the end of its travel while you hold pressure. Spin each wheel by hand to confirm the brakes are not dragging. Then, in a safe, low-speed area, test the brakes gently before riding normally.

Troubleshooting and When to Visit a Shop

If the lever or pedal will not firm up after several rounds of bleeding, or if it only firms up temporarily after pumping, there is still air somewhere in the system — or fluid is bypassing internally. Persistent bubbles at the bleeder, or fluid seeping from the master cylinder or caliper, also warrant a closer look before the bike goes back on the road.

One important caveat applies specifically to this ABS-equipped Grom: a routine bleed through the caliper bleeders is fine for refreshing fluid, but if the reservoir ever ran dry, or if the ABS unit or its lines were disconnected, air may have entered the ABS modulator itself. Purging that requires a dealer-level procedure or diagnostic tool, and the bike should go to a shop rather than being bled further at home.

Related Shopping Categories

Shop Brake Fluid for a 2020 Honda Grom ABS Motorcycle.

Shop Brake Lines for a 2020 Honda Grom ABS Motorcycle.

Shop Brake Pads for a 2020 Honda Grom ABS Motorcycle.

Shop Stands for a 2020 Honda Grom ABS Motorcycle.

Shop Brake Tools for a 2020 Honda Grom 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.