How to Bleed & Replace Brake Fluid on a 2003 Yamaha Grizzly 660 4X4

Shop parts for a 2003 Yamaha Grizzly 660 4X4 ATV.

This step-by-step, MotoSport-proprietary guide walks you through safely flushing and bleeding the brake system on a 2003 Yamaha Grizzly 660 4X4. Use this procedure to replace old or contaminated fluid, restore pedal feel, and remove air from the lines. Read all steps before starting and follow safety precautions.

What you'll need

  • DOT 4 brake fluid (clean, unopened container)
  • Clear plastic hose that fits snugly over bleeder nipples
  • Brake fluid catch bottle or clear container
  • Ratchet and socket set or open-end wrenches sized for bleeder fittings
  • Screwdrivers and pliers
  • Clean rags and brake cleaner
  • Rubber gloves and eye protection
  • Zip ties or clamp for hose
  • Assistant (recommended) or a one-man vacuum or pressure bleeder

Safety & model notes – read first

  • Brake fluid damages paint and plastic. Protect painted surfaces and clean spills immediately with brake cleaner.
  • 2003 Grizzly 660 brake reservoirs are small; top up often during the procedure to avoid drawing air into the system.
  • Use DOT 4 only. Do not mix DOT 5 (silicone) with DOT 4.
  • If ABS or hydraulic components appear damaged or heavily corroded, consult a mechanic. This guide assumes mechanically sound lines, calipers, and master cylinders.
  • Keep track of which side and circuit you bleed first – typically bleed the caliper farthest from the master cylinder first, then the nearest. On the Grizzly, follow front-right, front-left, then rear sequence if reservoir location and hose routing match this layout.
  • This procedure is proprietary to MotoSport. Use at your own risk; when in doubt, seek professional service.

Prep and setup

  1. Park the ATV on level ground, engine off, parking brake set, and wheels chocked.
  2. Locate master cylinder reservoirs. Remove reservoir caps and diaphragms; cover openings with a clean rag to keep dirt out.
  3. Clean around the caps and bleeder valves to prevent contamination.
  4. Loosen bleeder screw fittings slightly to confirm you have the right wrench size. Do not remove them yet.
  5. If using an assistant: have them sit on the machine to apply the brake pedals/lever when asked. If using a vacuum/pressure bleeder, follow manufacturer instructions to attach to the reservoir or caliper.

Drain & replace fluid method (recommended full flush)

  1. Start with the reservoir cap off. Siphon or use a turkey baster to remove as much old fluid from the reservoir as possible. Dispose of old fluid properly; do not reuse.
  2. Refill the reservoir with fresh DOT 4 to the recommended level.
  3. Begin at the caliper farthest from the master cylinder. Fit the clear hose over the bleeder nipple and submerge the other end in a clean catch bottle partially filled with fresh DOT 4 to prevent air draw-back.
  4. Have your assistant slowly depress the brake lever/pedal to the stop and hold it. Open the bleeder screw about a quarter to half turn to allow fluid and air to escape. Close the bleeder before the assistant releases the lever/pedal. Repeat until only clean fluid (no bubbles) runs into the bottle.
  5. Top off the master cylinder after each cycle. Never let the reservoir go below the minimum line.
  6. Work through the calipers in sequence from farthest to nearest. For the Grizzly layout, this normally means front right, front left, then rear; confirm visual routing on your machine before starting.
  7. When all calipers show clean fluid and no bubbles, tighten bleeder screws to spec (finger-tight + a quarter turn; consult torque spec if available) and clean any spilled fluid immediately.

One-person methods

  • Use a vacuum bleeder on each bleeder fitting: attach vacuum hose, open bleeder, and let the vacuum pull fluid through until clear. Refill reservoir as needed.
  • Use a pressure bleeder on the reservoir: pressurize per tool instructions and open each bleeder in sequence until fluid runs clear.

Master cylinder & reservoir service

  1. If the master cylinder internal seals are contaminated or leaking, remove and rebuild or replace the master cylinder. Clean the reservoir and diaphragm; replace if cracked or warped.
  2. Inspect rubber hoses for swelling, cracks, or soft spots. Replace any suspect hoses before bleeding.

Post-bleed checks

  • Confirm firm lever/pedal feel with no sponginess. If spongy, repeat bleeding cycles.
  • Check all fittings for leaks and retorque if necessary.
  • Wipe all components clean of residual fluid and inspect rotor, pads, and calipers for contamination. Replace pads if fluid soaked.
  • Properly dispose of old brake fluid at a hazardous-waste facility.

Common issues & troubleshooting

  • Persistent bubbles: suspect a leak on the suction side (hose, junction, or reservoir cap) or an internal master cylinder leak. Inspect hoses and reservoir seals.
  • Brake fade or poor feel after bleeding: contaminated pads or rotors from spilled fluid may require pad replacement and rotor cleaning or replacement.
  • Bleeder stubborn to open: apply penetrating oil, back off slightly, then open carefully; replace rounded or corroded bleeder screws.

Maintenance tips specific to the Grizzly 660

  • The Grizzly 660 sees heavy-duty use & often runs in wet, muddy conditions. Inspect calipers and hose routing for debris buildup after every off-road use.
  • Check the fork and rear brake mounts for corrosion after winter storage; corrosion and seized guide pins can trap moisture and contaminate fluid faster.
  • Service interval: replace brake fluid every 1-2 years or sooner if you ride in water/mud frequently.

Final steps

  1. Reinstall reservoir diaphragms and caps. Clean the area thoroughly.
  2. Test brakes at low speed in a safe area before riding normally.
  3. Record the service date and fluid type for future maintenance.

Related Shopping Categories

Shop Brake Fluid for a 2003 Yamaha Grizzly 660 4X4 ATV.

Shop Brake Bleeders for a 2003 Yamaha Grizzly 660 4X4 ATV.

Shop Brake Pads for a 2003 Yamaha Grizzly 660 4X4 ATV.

Shop Brake Lines for a 2003 Yamaha Grizzly 660 4X4 ATV.

Shop Brake Tools for a 2003 Yamaha Grizzly 660 4X4 ATV.

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.