Bleeding the Brakes on a 2021 Honda Monkey ABS
Shop parts for a 2021 Honda Monkey ABS Motorcycle.
The 2021 Honda Monkey ABS packs a genuine hydraulic brake system into a very small package, and like any hydraulic system it depends on clean, air-free fluid to deliver a firm, predictable lever and pedal. Bleeding pushes fresh fluid through the lines while expelling trapped air, and it is a job a rider with basic hand tools and moderate confidence can handle at home. What follows walks through the Monkey's specific layout, the prep work that protects your bike, the procedure itself, and how to confirm the job is right before you ride.
Understand the Monkey's Brake Layout First
Your Monkey ABS uses hydraulic disc brakes at both ends. The front brake is a caliper fed by a master cylinder mounted at the lever, and the rear is a separate caliper fed by its own pedal-driven master cylinder. These are independent circuits — there is no linked or combined braking on this machine — so the front lever works only the front brake and the pedal works only the rear. Each circuit passes through an ABS modulator, and that is the one component that deserves caution. Flushing fluid out through the caliper bleeder valves is routine maintenance. Purging air that has worked its way into the ABS unit itself is not a garage procedure, and that situation belongs at a dealership.
Recognizing When a Bleed Is Due
The classic signal is a lever or pedal that feels spongy or soft, or one that now travels noticeably closer to the grip or to the end of its stroke than it used to. Dark, cloudy, or discolored fluid in the reservoir is another clear indicator. So is any recent work that opened the hydraulic system — new brake lines, caliper service, or master cylinder work all introduce air that must be removed.
Even with no symptoms at all, brake fluid absorbs moisture from the air over time. That moisture lowers the fluid's boiling point, and under hard or repeated braking it can turn to vapor in the lines and produce a soft, fading brake. Because of that, many riders refresh the fluid on a regular interval rather than waiting for the lever to go soft.
Tools and Supplies to Gather
- Fresh brake fluid of the type printed on the master cylinder reservoir cap, poured from a sealed container — an opened bottle that has been sitting absorbs moisture and should not go in your bike
- A box-end wrench that fits the bleeder valve snugly, so it will not round the hex
- A length of clear tubing that fits tightly over the bleeder nipple
- A small catch bottle for the old fluid
- Rags or shop towels, plus a cup of water for rinsing spills
- A syringe or turkey baster for drawing old fluid out of the reservoir
- The correct driver for the reservoir cap screws
- Optional but helpful: a one-way check-valve bleeder or a vacuum bleeder, which makes a solo job far less fiddly
Set Up Before You Open Anything
Get the bike securely upright on a stand so it cannot tip while you are working the lever. Turn the handlebars until the front reservoir sits level, since a tilted reservoir will spill as soon as the cap comes off. Then drape rags over the bodywork, the instrument area, and any painted surface below the reservoir. Brake fluid damages paint and plastic on contact, so wipe up any drip immediately and rinse the area with water rather than rubbing it in.
The Front Brake Bleeding Procedure
- Remove the reservoir cap and the diaphragm beneath it, setting them somewhere clean where they will not pick up grit.
- Draw most of the old fluid out of the reservoir with the syringe, leaving the bottom of the reservoir covered. Never let the reservoir run dry, or you will pull air straight into the system.
- Refill the reservoir with fresh fluid from your sealed container.
- Push the clear tubing onto the front bleeder valve and route the other end into the catch bottle, with the tube end submerged in a splash of fluid.
- Squeeze the front lever slowly and hold it against the grip.
- While holding the lever, open the bleeder about a quarter turn. Fluid and air will push out through the tube.
- Close the bleeder before you release the lever. Releasing with the bleeder open draws air back into the caliper.
- Check the reservoir level and top it off, then repeat the squeeze, hold, open, close, release cycle until the fluid in the tube runs clean and free of bubbles.
- Keep the reservoir at least half full throughout. If it drops low, stop and refill before continuing.
If your bike has two front calipers, bleed each one in turn. As a general practice, start with the caliper farthest from the master cylinder and work toward the closest one.
The Rear Brake Bleeding Procedure
- Open the rear master cylinder reservoir and draw out most of the old fluid, then top it up with fresh fluid.
- Fit the clear tubing over the rear caliper bleeder and lead it into the catch bottle.
- Press and hold the brake pedal down.
- Open the bleeder about a quarter turn with the pedal held, let fluid and air escape, then close the bleeder before releasing the pedal.
- Top off the reservoir and repeat until the fluid runs clean and bubble-free.
Finishing Up and Checking for Leaks
Once clean fluid is flowing at both ends, tighten each bleeder snugly with your box-end wrench. Snug is the goal — overtightening can damage the valve seat. Fill each reservoir to the level marking, reinstall the diaphragm and cap, and wipe down every surface that saw fluid. Then inspect the bleeder valves and the banjo fittings at the calipers and master cylinders for any weeping or dampness.
Test the Brakes Before Riding
With the bike still on the stand, squeeze the lever and press the pedal. Both should feel firm and consistent, not spongy, and neither should slowly sink while you hold steady pressure. Spin each wheel by hand to confirm the brakes are not dragging. Then, in a safe open area, test the brakes at low speed before riding normally.
When to Stop and See a Shop
If the lever will not firm up after several rounds of bleeding, if it only firms after pumping, or if bubbles keep appearing no matter how long you work, something is letting air in and the system needs professional attention. The same applies to fluid leaking from a master cylinder or caliper, or to any situation where the reservoir ran dry, a line was disconnected, or you suspect air reached the ABS unit — that last case generally requires a dealer-level procedure to purge correctly.
Related Shopping Categories
Shop Brake Fluid for a 2021 Honda Monkey ABS Motorcycle.
Shop Brake Lines for a 2021 Honda Monkey ABS Motorcycle.
Shop Brake Pads for a 2021 Honda Monkey ABS Motorcycle.
Shop Stands for a 2021 Honda Monkey ABS Motorcycle.
Shop Brake Tools for a 2021 Honda Monkey 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.
