Bleeding the Brakes on Your 2020 Honda Monkey
Shop parts for a 2020 Honda Monkey Motorcycle.
The 2020 Honda Monkey Z125M stops on hydraulic disc brakes at both ends. Up front there is a single disc and caliper fed by the lever-mounted master cylinder; at the rear there is a single disc and caliper fed by a pedal-driven master cylinder with its own small reservoir. There is no linked or combined braking here, so the two circuits are completely independent and each one has to be bled on its own. That is good news in the garage — a stubborn bubble on one end will not contaminate the other — but it also means a firm front lever tells you nothing about the state of the rear.
One caveat before you pick up a wrench: if your particular Monkey is the ABS-equipped variant, a routine bleed at the calipers is still the right way to refresh fluid, but air that has worked its way into the ABS unit itself generally requires a dealer-level procedure. If the reservoir has ever run dry, or a line or the ABS unit has been off the bike, let a shop handle it.
Why Fluid Ages and What Tells You It Is Time
Brake fluid is hygroscopic, meaning it pulls moisture out of the air over time. That moisture does two bad things: it lowers the fluid's boiling point, so hard, repeated braking can boil the fluid and give you a spongy lever and fade right when you need brakes most, and it corrodes the internals of the master cylinder and caliper. Many riders simply refresh the fluid on a schedule rather than waiting for a symptom.
Symptoms that should send you straight to the bleed bottle include a lever or pedal that feels soft or spongy, a front lever that now comes noticeably closer to the grip than it used to, fluid in either reservoir that looks dark, cloudy, or gritty, and any recent work that opened the hydraulic system — new lines, a caliper rebuild, or master cylinder service. A lever that firms up only after several quick pumps is a classic sign of air in the line.
Tools and Supplies to Have Ready
- Fresh brake fluid of the type printed on the master cylinder reservoir cap, from a sealed container — once a bottle is opened it starts absorbing moisture, so use new stock
- A box-end wrench that fits the bleeder valve snugly; a box-end grips better than an open-end and is less likely to round the hex
- A length of clear tubing that fits tightly over the bleeder nipple, plus a small catch bottle to hang it in
- Rags or shop towels, and a spray bottle of water for rinsing spills
- A syringe or turkey baster for pulling old fluid out of the reservoir
- The correct driver for the reservoir cap screws
- Optional but genuinely helpful: a one-way check-valve bleeder or a vacuum bleeder, either of which makes a solo job far less fiddly
Setting Up and Protecting the Finish
Get the Monkey securely upright on a stand so it cannot tip while you are working the lever. For the front circuit, turn the handlebar until the reservoir on the lever perch sits level — a tilted reservoir lets fluid spill the moment you crack the cap. Drape rags over the tank area, the plastics, and the instrument cluster, because brake fluid attacks paint and plastic on contact. If a drop does land somewhere it should not, wipe it up immediately and rinse the area with water rather than waiting until the end of the job.
Bleeding the Front Brake
- Wipe the reservoir cap and the area around it clean so grit cannot fall in, then remove the cap and the diaphragm.
- Use the syringe or baster to draw most of the old fluid out of the reservoir. Leave enough at the bottom that you are not pulling air into the master cylinder port.
- Top the reservoir up with fresh fluid from your sealed container.
- Push the clear tubing onto the front caliper bleeder and route the other end into the catch bottle, with the bottle positioned so the tube runs upward or level — a low loop traps air.
- Squeeze the front lever slowly and hold it against the grip.
- With the lever held, open the bleeder about a quarter turn with the box-end wrench. You will see fluid and possibly air bubbles travel down the tube.
- Close the bleeder before you release the lever. Releasing with the bleeder open draws air straight back into the caliper, which is the single most common way a home bleed goes wrong.
- Release the lever, then repeat the squeeze–hold–open–close–release cycle. Check the reservoir every few cycles and top it off — it must never run low enough to pull air in at the master cylinder.
- Keep going until the fluid coming through the tube is clean and free of bubbles, and the lever feels firm rather than spongy.
If your bike has two front calipers, bleed each one in turn, finishing the one you started with. As a general habit, start with the caliper farthest from the master cylinder and work toward the closest.
Bleeding the Rear Brake
The rear circuit on the Monkey works the same way with a different input. Locate the rear master cylinder reservoir, clean around its cap, and open it. Remove most of the old fluid, refill with fresh, and fit the tubing to the rear caliper bleeder. Then press and hold the brake pedal, crack the bleeder a quarter turn, close it, and release the pedal — in that order, every time. Keep the reservoir topped up as you go and continue until the fluid runs clean and bubble-free and the pedal feels solid underfoot.
Finishing, Testing, and When to Stop
When both circuits are done, snug the bleeder valves down firmly without overtightening — you are sealing a small tapered seat, not torquing a lug nut, and a stripped bleeder is a much bigger job than a bleed. Fill each reservoir to the level marking, reinstall the diaphragm and cap, and wipe down every surface you touched. Look closely at the bleeder valves and at the banjo fittings at the master cylinder and caliper for any weeping, then squeeze the lever and press the pedal and check again.
Before you ride, the lever and pedal should feel firm and consistent, and should hold pressure without slowly sinking while you keep a steady squeeze on them. Spin each wheel by hand to confirm the brakes are not dragging. Then test at low speed in a safe, empty area before riding normally.
Take the bike to a shop if the lever will not firm up after several honest attempts, if it only firms up when you pump it, if bubbles keep appearing no matter how long you bleed, if you find fluid weeping from the master cylinder or a caliper, or if there is any chance air entered an ABS unit. Those are the situations where a proper diagnosis beats another round of bleeding.
Related Shopping Categories
Shop Brake Fluid for a 2020 Honda Monkey Motorcycle.
Shop Brake Lines for a 2020 Honda Monkey Motorcycle.
Shop Brake Pads for a 2020 Honda Monkey Motorcycle.
Shop Stands for a 2020 Honda Monkey Motorcycle.
Shop Brake Tools for a 2020 Honda Monkey 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.
