Bleeding the Brakes on a 1991 Honda NT650 Hawk GT
Shop parts for a 1991 Honda NT650 - Hawk GT Motorcycle.The 1991 Honda NT650 Hawk GT uses hydraulic disc brakes at both ends, and this model is a conventional non-ABS, non-linked system. That makes the job refreshingly direct: you are flushing old fluid out of the front and rear circuits and removing any air that has entered. Because the rear brake is hydraulic rather than a mechanical drum, it is bled in the same basic way as the front. Work methodically, keep the reservoir from running dry, and treat every drop of brake fluid as something that can damage paint and plastic.
Why and When the Hawk GT Needs a Brake Bleed
Bleeding is not only for a brake system that has been opened for a line replacement, caliper service, or master cylinder work. Brake fluid absorbs moisture over time, which lowers its boiling point and can contribute to brake fade under hard or repeated use. Even if the bike stops well, dark or cloudy fluid in the reservoir is a sign that fresh fluid is overdue. A spongy lever, a pedal that feels soft, or a lever that now pulls closer to the grip than it used to are all clues that air or degraded fluid is affecting the system.
Many riders refresh brake fluid on a regular schedule as preventive maintenance, then bleed again any time the hydraulic system has been opened. On a Hawk GT, the front and rear systems are separate, so each one must be serviced on its own. If the lever or pedal feels inconsistent after a fluid flush, do not assume the job is finished; air may still be working its way through the circuit.
Tools and Supplies to Have Ready
- Fresh brake fluid of the type marked on the master cylinder reservoir cap, from a sealed container
- A box-end wrench that fits the bleeder valve
- Clear tubing that fits snugly over the bleeder valve
- A small catch bottle for used fluid
- Rags or shop towels, plus a syringe or turkey baster for removing old fluid from the reservoir
- A screwdriver or driver that fits the reservoir cap screws
- Optional: a one-way check-valve bleeder or vacuum bleeder to make one-person bleeding easier
Use only fluid from a sealed container, and do not reuse fluid that has been sitting open or drained from the system. The reservoir cap tells you which fluid family is correct for this bike; follow that marking rather than guessing. Keep the catch bottle low and stable so the clear tubing stays submerged at its end, which helps you see bubbles and prevents fluid from splashing.
Preparing the Bike and Protecting Surfaces
Support the Hawk GT securely upright on a stand so it cannot tip while you are working the lever or pedal. Turn the handlebars so the front reservoir sits level before you open it; a tilted reservoir can spill fluid as soon as the cap comes off. Cover painted bodywork, plastic panels, and the instrument area with rags, because most brake fluids damage paint and plastic on contact. If a spill happens, wipe it up immediately and rinse the area with water.
Before opening the reservoir, clean around the cap so dirt does not fall into the fluid. Have your catch bottle and tubing positioned before you loosen the bleeder. A little preparation here prevents the most common messes and keeps contaminated fluid from finding its way onto finished surfaces.
Bleeding the Front Brake
The front brake is the circuit you will feel most through the lever, so take your time and watch the tubing closely. If your front brake has more than one caliper, bleed each caliper in turn and treat each one as its own bleed point. As a general practice, start with the caliper farthest from the master cylinder if the layout gives you a choice.
- Open the front reservoir and use a syringe or turkey baster to remove most of the old fluid. Do not let the reservoir run dry.
- Refill the reservoir with fresh fluid of the type marked on the cap.
- Attach the clear tubing to the front bleeder valve and route the other end into the catch bottle.
- Squeeze and hold the front brake lever.
- Open the bleeder about a quarter turn to let fluid and air escape through the tubing.
- Close the bleeder before releasing the lever. Releasing with the bleeder open can draw air back into the caliper.
- Repeat the squeeze, hold, open, close, and release sequence until fresh, clean, bubble-free fluid comes through the tube.
- Keep topping off the reservoir throughout the process so it never runs low enough to draw air into the master cylinder.
- When the fluid runs clear and no bubbles appear, close the bleeder snugly without overtightening it.
- Refill the reservoir to the correct level marking, then reinstall the diaphragm and cap.
Bleeding the Rear Brake
The Hawk GT’s rear brake is hydraulic, so it uses the same basic procedure with the rear pedal instead of the front lever. Set the bike upright and make sure the rear reservoir is level before opening it. Clean the cap area, remove most of the old fluid, and top off with fresh fluid from the sealed container.
Fit the clear tubing over the rear bleeder valve and route it into the catch bottle. Press and hold the rear brake pedal, open the bleeder about a quarter turn, then close it before releasing the pedal. Repeat until the fluid in the tube is clean and free of bubbles, topping off the reservoir as you go. Finish by tightening the bleeder snugly without overtightening, filling the reservoir to the correct level, and reinstalling the diaphragm and cap. Wipe up any spilled fluid immediately and rinse the area with water if needed.
Finishing Up and Testing Before You Ride
After both circuits are bled, check the bleeder valves and the banjo fittings at the master cylinder and caliper for leaks. A dry paper towel wiped around each fitting will show fresh fluid quickly. The front lever and rear pedal should feel firm and consistent, not spongy, and they should not slowly sink while you hold steady pressure. Spin each wheel to confirm the brakes are not dragging, then test the brakes at low speed in a safe area before riding normally.
If the lever or pedal will not firm up after several bleeding attempts, if it firms only after pumping, if bubbles keep appearing, or if fluid is leaking from the master cylinder or caliper, stop and have the system inspected. This Hawk GT has no ABS unit or linked brake system to complicate the bleed, so a standard caliper bleed is the correct approach; a persistent problem points to a seal, fitting, or bleeding technique issue that should be diagnosed before the bike is ridden.
Related Shopping Categories
Shop Brake Fluid for a 1991 Honda NT650 - Hawk GT Motorcycle.
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Shop Brake Tools for a 1991 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.
