How To Bleed 2018 Kawasaki EX400 - Ninja 400 Motorcycle Brakes

Bleeding the Brakes on a 2018 Kawasaki Ninja 400

Know the Layout Before You Loosen Anything

The 2018 Kawasaki EX400 — the Ninja 400 — runs hydraulic disc brakes at both ends, so the front lever and the rear pedal each push fluid through a sealed circuit. The front master cylinder lives on the right handlebar with a small reservoir under a screw-held cap, and the rear master cylinder sits down near the right footpeg with its own reservoir. ABS was offered as an option on this model year, so confirm which version you have before you start; the ABS ring at the wheel and the dash indicator are the quickest tells. On a non-ABS Ninja 400, a straightforward bleed at the caliper is the whole job. On an ABS-equipped bike, refreshing fluid through the caliper bleeders works the same way, but if the reservoir has ever run dry, or the ABS unit or its lines have been disconnected, air can sit where a hand bleed will not reach it. That situation calls for a dealer-level procedure, not a longer session in the garage.

When a Bleed Is Actually Due

Brake fluid is hygroscopic, meaning it absorbs moisture from the air over time. That moisture lowers the fluid's boiling point, and a boiling fluid creates vapor that behaves exactly like air in the line — the lever goes soft right when you need it most, typically during hard or repeated braking. Many riders simply refresh the fluid on a regular interval rather than waiting for a symptom.

Beyond scheduled refresh, bleed the Ninja 400 whenever the lever pulls closer to the grip than it used to, the pedal feels spongy or travels further than normal, the fluid in either reservoir looks dark or cloudy, or you have just opened the hydraulic system for new lines, caliper work, or master cylinder service. Any of those means air or contaminated fluid is in the circuit.

Gather Tools and Supplies

• Fresh brake fluid of the type printed on the master cylinder reservoir cap, poured from a sealed container — an opened bottle has already begun absorbing moisture
• A box-end wrench that fits the bleeder valve snugly, so it will not round the hex
• Clear tubing sized to fit tightly over the bleeder nipple
• A small catch bottle to hang the tubing into
• Rags or shop towels, plus a cup of water for rinsing spills
• A syringe or turkey baster for lifting 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 awkward

Set Up the Bike and Shield the Finish

Get the Ninja 400 held securely upright on a stand so neither wheel can tip or roll. Turn the handlebars until the front reservoir sits level, because an angled reservoir will spill the moment the cap comes off. Then drape rags over the tank, the upper fairing, the instrument cluster, and anything else below the reservoir.

This matters more than it sounds. Brake fluid attacks paint and many plastics on contact, and a single drip left sitting will leave a permanent mark. If a spill does happen, wipe it up immediately and rinse the area with water rather than waiting until the job is finished.

The Bleeding Procedure, Step by Step

1. Support the bike upright and level the front reservoir as described above.
2. Remove the reservoir cap and the rubber diaphragm beneath it, and set them somewhere clean where they will not pick up grit.
3. Use the syringe or baster to draw most of the old fluid out of the reservoir. Leave enough in the bottom that you are not introducing air at the master cylinder port.
4. Refill with fresh fluid from the sealed container, leaving the reservoir comfortably full.
5. Push the clear tubing onto the front caliper bleeder and route the other end into the catch bottle, with the bottle positioned so the tubing runs upward before it drops — that keeps an air pocket from siphoning back.
6. Squeeze the front lever and hold it firmly against the grip.
7. With the lever held, crack the bleeder about a quarter turn. Fluid and any trapped air will push out through the tubing.
8. Close the bleeder fully before you release the lever. Releasing first draws air back in through the open valve, which undoes the work.
9. Repeat the squeeze–open–close–release cycle, topping the reservoir off every few cycles so it never runs low enough to pull air into the master cylinder.
10. Keep going until the fluid arriving in the tubing is clean and free of bubbles, then close the bleeder snugly — firm, not overtightened, since the valve body is small and easy to damage.
11. If your bike has two front calipers, bleed each one in turn rather than trying to do both at once. As a general practice, start with the caliper farthest from the master cylinder and work toward the closest.
12. Move to the rear. The sequence is identical: top off the rear reservoir, fit the tubing to the rear caliper bleeder, press and hold the pedal, open the bleeder a quarter turn, close it, then release. Continue until the fluid runs clean and bubble-free.

Buttoning It Up

Once both circuits are bled, confirm each bleeder is snug, then fill each reservoir to the level marking on the body — not to the brim, since the fluid needs room to expand. 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; a damp fitting means something is not seated properly and needs attention before the bike moves.

Test Before You Ride

The lever and pedal should feel firm and consistent, and should hold that feel when you squeeze or press steadily for several seconds. A lever that slowly sinks toward the grip under constant pressure is a sign of remaining air or an internal leak. Spin each wheel by hand to confirm the brakes are not dragging, then ride slowly in a safe, open area and apply each brake gently before trusting them at speed.

When to Stop and Take It to a Shop

If the lever will not firm up after several honest bleeding attempts, if it only firms after pumping, if bubbles keep appearing no matter how long you work, or if fluid is seeping from the master cylinder or a caliper, stop and have the bike inspected. The same applies to any ABS-equipped Ninja 400 where the reservoir ran dry or the ABS unit was disturbed, and to any bike with a linked or combined system that uses extra bleed points and a specific sequence. Those are not failures of technique — they are simply jobs that need the right equipment.

Related Shopping Categories

Shop Brake Fluid for a 2018 Kawasaki EX400 - Ninja 400 Motorcycle.

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Shop Stands for a 2018 Kawasaki EX400 - Ninja 400 Motorcycle.

Shop Brake Tools for a 2018 Kawasaki EX400 - Ninja 400 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.