Bleeding the Brakes on a 1990 Honda NT650 Hawk GT

Shop parts for a 1990 Honda NT650 - Hawk GT Motorcycle.

The 1990 Honda NT650 Hawk GT has a hydraulic front disc brake and a hydraulic rear disc brake. It has no ABS unit and no linked-brake plumbing, so the two circuits are bled separately in much the same way. That simplicity helps a home mechanic, but brakes remain safety-critical: a little air or a reservoir run dry can turn a firm lever soft. Work methodically, protect the bike from spilled fluid, and confirm the result before riding.

Why and When to Bleed the Hawk GT Brakes

Bleed the brakes when the front lever or rear pedal feels spongy, when the lever pulls closer to the grip than before, or when fluid in either reservoir looks dark or cloudy. A bleed is also needed after any work that opened the hydraulic system, such as new lines, caliper service, or master cylinder repair. Even without symptoms, brake fluid absorbs moisture over time. That moisture lowers the fluid’s boiling point and can cause fade under hard use, so many riders refresh it on a schedule. If you do not know when the fluid was last changed, a flush is a sensible starting point.

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 snugly.
  • A length of clear tubing that fits tightly over the bleeder nipple.
  • 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 a vacuum bleeder, which can make a one-person job easier.
  • A secure stand or support to hold the motorcycle upright.

Preparing the Bike and the Work Area

Support the Hawk GT securely so it cannot tip while you press the lever or pedal. For the front circuit, turn the handlebars so the front reservoir sits level before opening it; a tilted reservoir can spill as soon as the cap comes off. Keep the rear reservoir level too. Cover painted bodywork, plastic panels, the instrument area, and nearby surfaces with rags. Most brake fluids damage paint and plastic on contact, so wipe spills immediately and rinse the area with water if fluid reaches a painted or plastic surface. Work on one circuit at a time and keep the other reservoir capped.

Bleeding the Front Brake

  1. Clean the top of the front reservoir before opening it so dirt does not fall into the fluid.
  2. Remove the cap and diaphragm, then use the syringe or baster to draw most of the old fluid out of the reservoir. Do not let the reservoir run dry.
  3. Refill the reservoir with fresh fluid to the upper level marking.
  4. Fit the clear tubing over the front caliper bleeder and route the other end into the catch bottle with the tube end submerged in a little fluid if possible.
  5. Slowly squeeze the front lever and hold it. With the lever held, open the bleeder about a quarter turn. Fluid and air will travel down the tube.
  6. Close the bleeder before you release the lever. Releasing with the bleeder open can draw air back into the caliper.
  7. Check the reservoir level and top it off before repeating. Never let the level fall low enough to pull air into the master cylinder.
  8. Repeat the squeeze-hold-open-close-release cycle until fresh, clean fluid comes through the tube with no bubbles. Add fresh fluid as needed throughout.
  9. On this front caliper there is only one bleed point to work. On any multi-caliper front end, start with the caliper farthest from the master cylinder and bleed each caliper in turn, keeping the reservoir topped off.
  10. When the fluid runs clear and bubble-free, close the bleeder snugly and move on to the final checks.

Bleeding the Rear Brake

  1. Clean around the rear reservoir cap, open it, and remove most of the old fluid with the syringe or baster.
  2. Refill with fresh fluid to the correct level marking and keep the reservoir level.
  3. Attach the clear tubing to the rear caliper bleeder and route it into the catch bottle.
  4. Press and hold the rear brake pedal, open the bleeder about a quarter turn, and let fluid and air escape.
  5. Close the bleeder before releasing the pedal.
  6. Top off the rear reservoir, then repeat the press-hold-open-close-release sequence until the fluid is clean and free of bubbles.
  7. Keep checking the reservoir after every few cycles; running it dry is the most common way to make a simple bleed take much longer.
  8. Finish by closing the bleeder snugly and checking the reservoir level.

Finishing Up and Checking for Leaks

Once both circuits are bled, tighten each bleeder snugly without overtightening; the goal is a sealed fitting, not a crushed one. Fill each reservoir to the correct level marking, reinstall the diaphragm and cap, and wipe away any fluid that escaped during the job. Check the bleeder fittings and the banjo fittings at the calipers and master cylinders for weeping or wetness. A clean, dry fitting after several lever or pedal applications is a good sign. If you see fluid at a fitting, do not ride until it is corrected.

Testing Before You Ride

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 and confirm the brake is not dragging. With the bike upright and in a safe area, test the brakes at low speed before riding normally. If either brake feels different from what you expect, stop and investigate rather than assuming it will improve.

If the Brakes Still Feel Soft

A lever or pedal that will not firm up after several careful bleeding attempts, one that firms only after pumping, persistent bubbles in the clear tube, or fluid leaking from a master cylinder or caliper are reasons to stop and diagnose further. Because the 1990 Hawk GT has no ABS unit and no linked-brake system, you do not have to deal with a dealer-only ABS bleed sequence on this model. If air has entered a system with ABS or linked brakes on another bike, or if you cannot find the source of a soft lever, have the motorcycle inspected by a qualified shop. On this Hawk GT, a firm, stable lever and pedal after a clean, bubble-free bleed are the confirmation you are looking for.

Related Shopping Categories

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Shop Brake Tools for a 1990 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.