Bleeding the Brakes on a 2020 Kawasaki Ninja 400 ABS
Shop parts for a 2020 Kawasaki EX400 - Ninja 400 ABS Motorcycle.The 2020 Kawasaki EX400 — the Ninja 400 ABS — runs hydraulic disc brakes at both ends, with an anti-lock braking system in the loop. That means there are two separate hydraulic circuits to service: the front, fed by the master cylinder on the right handlebar, and the rear, fed by the pedal master cylinder tucked low on the right side of the bike. Neither circuit is linked to the other, so each is bled on its own. This guide walks you through refreshing the fluid and purging air from both circuits in your own garage, and it flags the one situation where the ABS hardware means the job should go to a shop instead.
When a Bleed Is Due
The most obvious trigger is feel. A front lever that comes back closer to the grip than it used to, or that feels spongy rather than solid, is telling you air is in the system. The same goes for a rear pedal with a soft, vague travel. Any lever or pedal that slowly sinks toward the end of its stroke while you hold steady pressure is another red flag.
Fluid condition matters just as much as feel. Pop the reservoir cap and look: fresh fluid is clear and nearly colorless, while fluid that has been in service for a few seasons turns amber, then dark and cloudy. Brake fluid is hygroscopic, meaning it pulls moisture out of the air over time. That moisture lowers the fluid’s boiling point, and under hard or repeated braking it can boil into vapor — which behaves exactly like air in the lines and gives you a long, soft lever right when you need the brakes most. Many riders simply refresh the fluid on a regular interval rather than waiting for symptoms.
Finally, any job that opened the hydraulic system calls for a bleed afterward: new brake lines, a caliper rebuild or replacement, master cylinder work, or a reservoir that ran dry. On the Ninja 400 ABS, that last case deserves special attention — more on that below.
Tools and Supplies to Gather
- Fresh brake fluid of the type printed on the master cylinder reservoir cap, from a sealed container. Do not substitute a different type.
- A box-end wrench that fits the bleeder valve snugly — a six-point box end grips best and is less likely to round the valve.
- A length of clear tubing that fits tightly over the bleeder nipple, plus a small catch bottle to route it into.
- Rags or shop towels, and a syringe or turkey baster for pulling 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, either of which makes a solo job much easier.
Setting Up Safely
Get the bike supported securely upright on a stand so it cannot tip while you are working the lever. For the front circuit, turn the handlebars until the reservoir on the right bar sits level — an angled reservoir will spill. Before you open anything, drape rags over the tank, the upper fairing, the instrument cluster, and the surrounding plastics. Brake fluid attacks paint and many plastics on contact, and a single stray drip can leave a permanent mark. If a spill does happen, wipe it up immediately and rinse the area with water.
Work in a well-ventilated space and keep the fluid container capped when you are not pouring from it, since fresh fluid starts absorbing moisture the moment it meets open air.
Bleeding the Front Brake
- Remove the reservoir cap and diaphragm. Use the syringe or baster to draw most of the old fluid out of the reservoir, but stop before the level drops near the bottom port — you do not want to pull air into the master cylinder.
- Top the reservoir up with fresh fluid from the sealed container.
- Slip the clear tubing over the front caliper bleeder valve and route the other end into the catch bottle, with the bottle positioned so the tubing runs upward for a stretch before dropping — this helps you see bubbles travel.
- Fit the box-end wrench onto the bleeder. Squeeze the front lever and hold it firm.
- With the lever held, crack the bleeder about a quarter turn. Fluid and any trapped air will push out through the tubing. Watch the tube, not the reservoir, while the valve is open.
- Close the bleeder before you release the lever. Releasing with the valve open draws air back in through the bleeder threads.
- Release the lever slowly, then check the reservoir level and top it off. Repeat the squeeze–hold–open–close–release cycle until the fluid coming through the tube runs clean and free of bubbles.
- If your bike has two front calipers, bleed each one in turn, one at a time, keeping the reservoir topped up between them. As a general practice, start with the caliper farthest from the master cylinder and work toward the closest.
Throughout the entire sequence, the reservoir must never run low enough to suck air. Check it after every few cycles and refill before it gets close to empty. Running it dry means starting over and pushing a fresh slug of air down the line.
Bleeding the Rear Brake
The rear circuit follows the same logic with the pedal in place of the lever. Remove the rear reservoir cap, draw out the old fluid, and refill with fresh. Attach the tubing and catch bottle to the rear caliper bleeder, fit the wrench, then press and hold the pedal, open the bleeder a quarter turn, close it, and release. Repeat until the fluid runs clean and bubble-free, topping the reservoir as you go. The rear reservoir is small, so check its level more often than you think you need to.
Finishing and Verifying the Job
When both circuits run clean, close each bleeder snugly — firm enough to seal, but do not overtighten and risk damaging the valve or its seat. Fill each reservoir to the level marking on the body, reinstall the diaphragm and cap, and wipe down every surface you touched. Inspect the bleeder valves and the banjo fittings at the master cylinders and calipers for any weeping or dampness; a leak here means the fitting needs attention before you ride.
Now test. The front lever should feel firm and consistent, and the rear pedal should have a solid, positive travel. Hold steady pressure on each for several seconds — neither should sink. Spin both wheels by hand to confirm the brakes are not dragging. Then, in a safe open area, test the brakes at low speed before riding normally.
Troubleshooting and When to Stop
If the lever will not firm up after several rounds of bleeding, or if it only firms up after you pump it a few times, air is still trapped somewhere. Persistent bubbles at the bleeder usually mean air is being drawn in past the bleeder threads or the tubing is not sealing — check both before continuing.
On this ABS-equipped Ninja 400, there is one important limit. A routine flush through the caliper bleeders is fine, but if the reservoir 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 no amount of lever pumping at the caliper will clear it. In that case, or if you see fluid leaking from the master cylinder or a caliper, stop and take the bike to a shop. Firm, reliable brakes are worth the wait.
Related Shopping Categories
Shop Brake Fluid for a 2020 Kawasaki EX400 - Ninja 400 ABS Motorcycle.
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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.
