How To Bleed 1989 Honda NT650 - Hawk GT Motorcycle Brakes

Bleeding the Brakes on a 1989 Honda NT650 Hawk GT

How the Hawk GT's Brakes Are Configured

The 1989 NT650 Hawk GT stops on hydraulic disc brakes at both ends. The front system is driven by the lever on the right handlebar and its own master cylinder and reservoir; the rear is driven by the foot pedal and a separate master cylinder with its own fluid supply. There is no ABS unit on this machine and no linked or combined braking system, so the two circuits are completely independent of each other. That independence is what makes this a friendly bike to service at home: you bleed the front, then you bleed the rear, and neither job affects the other. There is no diagnostic tool to plug in and no required sequence across circuits. If your particular Hawk GT has been modified with different calipers, a different master cylinder, or converted components, look over what is actually bolted to the bike before you begin and treat each circuit on its own merits.

Why and When the Fluid Needs Replacing

Brake fluid is hygroscopic, meaning it pulls moisture out of the air over time, even through sealed rubber components. Moisture does two harmful things: it lowers the fluid's boiling point, so hard or repeated braking can boil the fluid and give you a lever that goes soft or long exactly when you need it most, and it corrodes the internals of the master cylinder and caliper. That is why many riders refresh the fluid on a schedule whether or not anything feels wrong.

Bleed the system sooner if the lever feels spongy or pulls closer to the grip than it used to, if the pedal feels soft or travels further, if the fluid visible in the reservoir looks dark, cloudy, or gritty, or if you have just done work that opened the hydraulics — new lines, a caliper rebuild, a master cylinder service, or a pad change that pushed the pistons back. Any of those can introduce air, and air is what a bleed removes.

Tools and Supplies to Collect First

• 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 box-end grips the flats far better than an open-end and is much less likely to round the bleeder.
• 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 helpful: a one-way check-valve bleeder or a vacuum bleeder, either of which makes a solo bleed much less fiddly.

Setting Up and Protecting the Finish

Get the bike held securely upright on a stand so it cannot tip while you are leaning on the lever. For the front circuit, turn the handlebars until the reservoir on the master cylinder sits level; a tilted reservoir will spill fluid the moment the cap comes off. Before you open anything, drape rags over the tank, the fairing or bodywork, the instrument cluster, and the area directly under the reservoir. 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, blot it up immediately and flood the area with water rather than wiping it around.

Bleeding the Front Brake, Step by Step

1. Wipe the reservoir cap clean so no dirt falls in, then remove the cap and the diaphragm beneath it.
2. Draw most of the old fluid out of the reservoir with the syringe or baster. Leave enough to cover the port at the bottom — never let the reservoir run dry, or you will pump air straight into the line.
3. Top the reservoir up with fresh fluid from the sealed container.
4. Slip the box-end wrench over the bleeder valve, then push the clear tubing onto the nipple and route the other end into the catch bottle. A little fluid in the bottle stops air being drawn back up the tube.
5. Squeeze the front lever slowly and hold it against the grip.
6. Open the bleeder about a quarter turn. Fluid and any trapped air will push out through the tube. Watch the tube, not the lever.
7. Close the bleeder fully before you release the lever. Releasing with the bleeder open pulls air back into the caliper.
8. Let the lever return slowly, then check the reservoir level and top it off.
9. Repeat the squeeze, open, close, release cycle, topping off as you go, until the fluid coming through the tube runs clean and free of bubbles.
10. If your bike carries two front calipers, bleed each one in turn, starting with the caliper farthest from the master cylinder and finishing with the closer one.

Bleeding the Rear Brake

The rear circuit works the same way with the pedal in place of the lever. On the Hawk GT the rear master cylinder is mounted low on the frame with a remote reservoir, so check that reservoir's level often — it holds less than the front and can run low quickly during a flush. Press and hold the pedal, crack the rear bleeder, close it, then release. Keep the reservoir topped until the fluid runs clean and bubble-free.

Finishing the Job Correctly

Close the bleeder snugly with the box-end wrench. Snug is enough — these are small fittings and overtightening can damage the seat. Fill the reservoir to the level marking molded into it, reinstall the diaphragm and cap, and wipe down every surface you touched. Rinse any suspect area with water. Then inspect the bleeder and the banjo fittings at the master cylinder and caliper for weeping, and pump the lever and pedal a few times to push the pads back out against the rotors.

Testing 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 and confirm the brake is not dragging. Then, in a safe open area, test the brakes at low speed before riding normally. If anything feels vague, stop and investigate rather than riding it out.

When to Hand It to a Shop

If the lever will not firm up after several full bleeding cycles, if it only firms after a few quick pumps, if bubbles keep appearing no matter how long you bleed, or if you find fluid weeping from the master cylinder or caliper, stop and have the system inspected. Air that keeps returning usually means a seal is failing or air is being drawn past the bleeder threads. Because this Hawk GT has no ABS unit, there is no hidden module to trap air, but any bike that has been modified with ABS or a linked system has extra bleed points and a required sequence — that work belongs with a shop that knows the procedure.

Related Shopping Categories

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Shop Brake Tools for a 1989 Honda NT650 - Hawk GT 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.