How to Bleed the Brakes on a 2020 Kawasaki Ninja 400
Shop parts for a 2020 Kawasaki EX400 - Ninja 400 Motorcycle.
What the EX400 Brake Layout Means for This Job
Your 2020 Kawasaki Ninja 400 runs hydraulic disc brakes at both ends. The front lever and the rear pedal each push fluid from their own reservoir through a hose to a caliper, and each circuit has its own bleeder valve at the caliper. Because both ends are hydraulic, both can be bled at home with hand tools — there is no cable-operated drum brake on this bike to work around.
One detail to settle before you begin: some 2020 EX400s were built with ABS and some were not. A routine fluid flush through the caliper bleeders works the same either way. What changes is the failure case. If a reservoir ever ran dry, or if a line or the ABS unit itself was disconnected, air can end up inside the ABS hardware where a lever-and-bleeder routine will never reach it. That job belongs at a shop with the correct diagnostic equipment. The Ninja 400 does not use linked brakes, so the front and rear circuits are independent and can be serviced one at a time in either order.
Signs You Need a Bleed — and Why Fluid Ages
A spongy lever, a pedal that feels soft or travels farther than it used to, or a lever that pulls closer to the grip than it did last season all point to air in the system. So does fluid that looks dark, cloudy, or gritty in the reservoir sight glass. Any work that opened the hydraulic circuit — new lines, caliper service, master cylinder work — requires a bleed afterward, no exceptions.
Even with no symptoms, brake fluid absorbs moisture from the air over time. That moisture lowers the fluid's boiling point, and under hard or repeated braking the fluid can boil and generate gas, which shows up as a lever that fades toward the bar exactly when you need it most. Many riders refresh the fluid on a regular interval for that reason alone. If you cannot remember the last time yours was changed, this is a good season to do it.
Tools and Supplies to Gather First
- Fresh brake fluid of the type printed on the master cylinder reservoir cap, from a sealed container — opened fluid that has sat on the shelf absorbs moisture and should not go in the bike
- A box-end wrench that fits the bleeder valve snugly
- 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 syringe or turkey baster for pulling old fluid out of the reservoir
- The correct driver for the reservoir cap screws
A one-way check-valve bleeder or a vacuum bleeder makes the job much easier to do alone, since you are not juggling a wrench, a lever, and a bottle at the same time.
Setting Up the Bike and Protecting the Finish
Get the bike upright and stable on a stand so you can work the lever or pedal without it rocking. Turn the handlebar until the front reservoir sits level, because an angled reservoir will spill the moment you open the cap. Lay rags over the tank or bodywork, the instrument cluster, and the front fender before you touch anything.
Brake fluid attacks paint and many plastics on contact. If a drop lands anywhere it should not, wipe it immediately and rinse the area with water rather than waiting until you finish. Keep the cap on the reservoir whenever you are not actively adding fluid.
Step-by-Step: Bleeding the Front Brake
- Remove the reservoir cap and diaphragm, then use the syringe or baster to draw most of the old fluid out of the reservoir. Leave a little in the bottom so you do not push air into the master cylinder.
- Refill with fresh fluid to the upper level marking.
- Slide the clear tubing over the front caliper bleeder and route the other end into the catch bottle, with the tubing running upward before it drops so you can watch for bubbles.
- Squeeze the front lever slowly and hold it against the grip.
- Open the bleeder about a quarter turn with the box-end wrench. Fluid and air will push out through the tubing, and the lever will sink toward the grip.
- Close the bleeder fully before you release the lever. Releasing with the bleeder open pulls air back into the caliper.
- Release the lever, then repeat the squeeze-hold-open-close-release cycle. Check the reservoir level every few cycles and top it off — letting it run dry is the single most common way a simple bleed turns into a long one.
- Keep going until the fluid coming through the tubing is clean and free of bubbles, and the lever feels firm rather than spongy.
If your bike has two front calipers, bleed them one at a time and finish one completely before moving to the other. As a general practice, start with the caliper farthest from the master cylinder and work toward the closest.
Bleeding the Rear Brake
The rear circuit follows the same logic with a different input. Set the rear reservoir level, pull most of the old fluid out, and top it with fresh. Fit the tubing to the rear caliper bleeder, then press and hold the pedal instead of the lever. Open the bleeder a quarter turn, let the fluid and air escape, and close it before you let the pedal return. Repeat until the fluid runs clean and bubble-free and the pedal feels solid. Watch the rear reservoir level just as carefully as the front.
Finishing Up and Checking for Leaks
Snug the bleeder valves down firmly without overtightening — they seal on a small taper and can be damaged by excess force. Fill each reservoir to the correct level marking, reinstall the diaphragm and cap, and wipe down every surface you touched. Then inspect the bleeder valves and the banjo fittings at both the master cylinder and the caliper for weeping or wetness. A dry fitting after a few minutes of pressure is what you want to see.
Testing Before You Ride
With the bike still stationary, pull the front lever and press the rear pedal firmly. Both should feel firm and consistent, 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 at low speed, apply each brake individually and confirm it bites predictably before you ride normally.
When to Stop and Take It to a Shop
If the lever will not firm up after several full bleeding cycles, if it only firms up when you pump it, or if bubbles keep appearing no matter how long you work, stop and let a professional look at it. The same applies to fluid weeping from the master cylinder or caliper, and to any bike with ABS where the reservoir ran dry or a line was opened — air inside the ABS unit needs dealer-level equipment to purge correctly. There is no shame in handing off a brake job that will not come right; there is considerable risk in riding a bike whose lever still feels soft.
Related Shopping Categories
Shop Brake Fluid for a 2020 Kawasaki EX400 - Ninja 400 Motorcycle.
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Shop Stands for a 2020 Kawasaki EX400 - Ninja 400 Motorcycle.
Shop Brake Tools for a 2020 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.