How To Bleed 2025 Honda Grom ABS Motorcycle Brakes

Bleeding the Brakes on a 2025 Honda Grom ABS

What This Job Covers on the Grom ABS

The 2025 Honda Grom ABS uses hydraulic disc brakes at both ends and is equipped with ABS. The front lever and rear pedal operate separate hydraulic circuits, so each side has its own reservoir, master cylinder, line, and caliper. The Grom ABS is not linked: the front lever does not apply the rear brake, and the rear pedal does not apply the front. Bleed one circuit at a time.

This guide covers removing air and replacing old fluid, not replacing pads, rotors, calipers, or lines. Those repairs can create the need for a bleed, but once the hardware is assembled, the process below gets the system clean and firm again.

Why and When to Bleed

A soft or spongy lever, a vague pedal, or a lever that pulls closer to the grip are signs that air or degraded fluid is in the system. Dark or cloudy fluid is another reason to service it. Bleed after any work that opened the hydraulic system, such as new lines, caliper service, or master cylinder work.

Brake fluid absorbs moisture over time, lowering its boiling point and increasing the risk of brake fade under hard use. Many riders refresh fluid on a regular schedule even when the brakes feel normal. Use only fresh fluid from a sealed container, and use the fluid type marked on the master cylinder reservoir cap. Do not guess the type or substitute a different fluid.

Tools and Supplies to Stage First

• Fresh brake fluid of the type marked on the reservoir cap, from a sealed container
• A box-end wrench that fits the bleeder valve
• Clear tubing that fits snugly over the bleeder
• A catch bottle for old fluid
• Rags or shop towels
• A syringe or turkey baster for removing old fluid from the reservoir
• A screwdriver or driver that fits the reservoir cap screws

A one-way check-valve bleeder or vacuum bleeder can make one-person work easier, but the manual method below is enough with a helper or a way to hold pressure. Keep the catch bottle stable and route the tubing away from painted parts.

Setting Up Safely and Protecting the Bike

Support the Grom ABS securely upright on a stand so it cannot tip while you press the lever or pedal. Turn the handlebars so the front reservoir sits level before opening it. Cover painted surfaces, plastics, and the instrument area with rags. Most brake fluid damages paint and plastic on contact, so wipe spills immediately and rinse with water.

Keep the reservoir cap off only while servicing that circuit. Maintain the fluid level and keep dirt out. When moving between front and rear circuits, cap the one you are not working on.

Step-by-Step Bleeding Procedure

Work on one circuit at a time. On a system with more than one caliper on the same circuit, start with the caliper farthest from the master cylinder; the Grom ABS does not add that complication. The steps are the same for the front lever and rear pedal circuits.

1. Remove the reservoir cap and diaphragm. Use the syringe or turkey baster to remove most of the old fluid from the reservoir, but do not let the reservoir run dry. Leave enough fluid to keep air from entering the master cylinder.
2. Refill the reservoir with fresh fluid of the type marked on the cap. Keep the cap and diaphragm clean and nearby.
3. Fit the clear tubing snugly over the bleeder valve and route the other end into the catch bottle. Make sure the tubing stays on the bleeder and does not leak.
4. Squeeze and hold the front lever, or press and hold the rear pedal, depending on which circuit you are bleeding. Keep steady pressure on it.
5. Open the bleeder about a quarter turn. Fluid and air will move out through the tubing. Watch the tube, not the reservoir, while the bleeder is open.
6. Close the bleeder before you release the lever or pedal. This is the critical order: open, let fluid out, close, then release. Releasing first can draw air back into the caliper.
7. Release the lever or pedal, check the reservoir level, and top it off with fresh fluid. Repeat the squeeze–hold–open–close–release sequence until fresh, clean, bubble-free fluid comes through the tubing.
8. Keep topping off the reservoir throughout the process. If it runs low enough to draw air, you will have to start over and may push air into a place that is harder to clear.
9. When the front circuit is clean and bubble-free, close the front bleeder snugly and move to the rear circuit. Repeat the same steps using the rear pedal and rear bleeder.

If the reservoir runs dry, or if the ABS unit or its lines have been disconnected, air may have entered the ABS unit itself. A standard bleed through the caliper bleeders may not remove that air. Do not try to invent an ABS bleed sequence; have the bike serviced by a shop with the appropriate procedure or diagnostic tool.

Finishing Up and Checking for Leaks

When both circuits are done, tighten each bleeder snugly without overtightening. Fill each reservoir to the correct level marking, reinstall the diaphragm and cap, and clean any spilled fluid from the bike. Check for leaks at the bleeder and at the banjo fittings. Pump the lever and pedal a few times, hold pressure, and inspect again. A weep at a fitting or bleeder is a reason to stop and correct it before riding.

Testing Before You Ride

The lever and pedal should feel firm and consistent, not spongy, and they should not slowly sink while you hold steady pressure. Spin each wheel to confirm the brakes are not dragging. Test the brakes at low speed in a safe area before riding normally. If the lever or pedal changes feel after the test, or if either one needs pumping to firm up, do not ride the bike until the problem is resolved.

Troubleshooting and When to See a Shop

If the lever or pedal will not firm up after several attempts, firms only after pumping, keeps producing air bubbles, or fluid leaks from the master cylinder or caliper, stop and diagnose. A lever that will not firm up can point to trapped air, a worn master cylinder seal, or a fitting drawing air. Any situation where air may have entered the ABS unit, such as a reservoir that ran dry or disconnected ABS lines, should go to a shop. The Grom ABS is safety-critical, and a correct bleed is worth the extra time or professional service.

Related Shopping Categories

Shop Brake Fluid for a 2025 Honda Grom ABS Motorcycle.

Shop Brake Lines for a 2025 Honda Grom ABS Motorcycle.

Shop Brake Pads for a 2025 Honda Grom ABS Motorcycle.

Shop Stands for a 2025 Honda Grom ABS Motorcycle.

Shop Brake Tools for a 2025 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.