How to Bleed the Brakes on Your 2017 Honda CB300F

Shop parts for a 2017 Honda CB300F Motorcycle.

A soft lever, a pedal that travels farther than it used to, or fluid that has gone dark in the sight glass are all signs that the hydraulic system on your CB300F is asking for attention. Bleeding is the job that pushes old fluid and trapped air out of the circuit and replaces them with fresh fluid. On this bike it is a genuinely DIY-friendly task — no special tools, no computer, just patience and a clean workspace.

What the CB300F's Brake System Looks Like

The 2017 CB300F stops on hydraulic disc brakes at both ends. The front brake is a master cylinder mounted at the right handlebar, feeding a caliper at the front wheel. The rear is a separate circuit with its own pedal-actuated master cylinder, its own reservoir, and its own caliper. The two share nothing but the fluid specification, so each is bled independently and each must be verified independently afterward.

Some examples of this model were sold with anti-lock brakes. If yours is ABS-equipped, a routine fluid refresh through the caliper bleeder is still the normal procedure. What you should not attempt at home is purging air that has been pushed into the ABS unit itself — that happens when the reservoir runs dry, or when the unit or its lines have been disconnected. That job needs a dealer-level tool to cycle the pump. If your particular bike carries two front calipers rather than one, the steps below still apply; simply bleed each caliper in turn.

When a Bleed Is Warranted

Bleed when the lever or pedal feels spongy, when the lever pulls noticeably closer to the grip than it used to, or when the fluid in the reservoir looks dark, cloudy, or contaminated. Bleed after any work that opened the hydraulic system: new lines, a caliper rebuild, or master cylinder service. And bleed on a schedule even when nothing feels wrong, because brake fluid absorbs moisture from the air over time. Moisture lowers the fluid's boiling point, and a boiling fluid creates gas in the lines under hard, repeated braking — the classic fade that shows up exactly when you need the brakes most.

Tools and Supplies to Gather

  • Fresh brake fluid of the type marked on your 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 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 emptying the reservoir.
  • The correct driver for the reservoir cap screws.
  • Optional: a one-way check-valve bleeder or a vacuum bleeder, both of which make a solo job easier.

Setting Up Safely

Get the bike upright and stable on a stand so it cannot tip while you are working the lever. Turn the handlebars until the front reservoir sits level, then drape rags over the tank area, the plastics, and the instrument cluster. Brake fluid attacks paint and plastic on contact, so treat every drop as a spill: wipe it immediately and rinse the area with water. Keep the cap on the reservoir until you are ready to open it, and keep the bottle of fresh fluid capped between pours.

Bleeding the Front Brake

  1. Open the reservoir and use the syringe or baster to draw out most of the old fluid. Leave enough in the bottom that you do not expose the port to air.
  2. Top the reservoir up with fresh fluid from the sealed container.
  3. Push the clear tubing onto the front bleeder valve and route the other end into the catch bottle, with the bottle positioned so the tube's end stays submerged.
  4. Squeeze the front lever and hold it firm.
  5. Open the bleeder about a quarter turn. Fluid and air will push out through the tube. Watch the reservoir level as you do this.
  6. Close the bleeder before you release the lever. Releasing with the bleeder open draws air straight back into the caliper.
  7. Repeat the squeeze–hold–open–close–release cycle, topping the reservoir off as needed, until clean, fresh, bubble-free fluid comes through the tube.
  8. If your bike has two front calipers, repeat the whole sequence on the second caliper. As a general practice, start with the caliper farthest from the master cylinder and work toward the closest.

Bleeding the Rear Brake

  1. Empty and refill the rear reservoir the same way, keeping the level above the port.
  2. Fit the tubing to the rear bleeder and lead it into the catch bottle.
  3. Press and hold the brake pedal, crack the bleeder a quarter turn, then close it before releasing the pedal.
  4. Continue cycling until the fluid runs clear with no bubbles, checking the reservoir level after every few strokes.

Finishing Up and Checking for Leaks

Once clean fluid is flowing at both ends, close each bleeder snugly — firm, but never forced, since the caliper threads are easily damaged by overtightening. Fill each reservoir to the level marking, reinstall the diaphragm and cap, and wipe down every surface you touched. Then inspect the bleeder valves and the banjo fittings at the master cylinder and caliper for weeping or dampness. A leak here means the job is not finished.

Testing Before You Ride

The lever and pedal should feel firm and consistent, and should hold pressure without slowly sinking when you squeeze or press and hold. Spin each wheel by hand to confirm the brakes are not dragging. Then, in a safe, empty area, test the brakes at low speed before riding normally. If anything feels vague at that point, stop and diagnose rather than riding it out.

When to 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, if bubbles keep appearing no matter how long you bleed, or if you find fluid seeping from the master cylinder or a caliper, stop and have the system inspected. The same applies if the reservoir has ever run dry on an ABS-equipped bike, or if you are not confident about the sequence on a machine with additional bleed points. A brake system that is not right is not a system to ride on.

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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.