How to Bleed & Replace Brake Fluid on a 2000 Yamaha BigBear 400 4x4

Shop parts for a 2000 YAMAHA BIGBEAR400 ATV.

This MotoSport guide walks you through a reliable, safe brake fluid change and bleed procedure for the 2000 Yamaha BigBear 400 4x4 (MMY). Follow every safety step, work cleanly, and take your time to ensure firm, consistent brakes when you finish.

What you'll need

  • Recommended brake fluid (check your owner's manual; DOT 3 or DOT 4 are common) — never mix glycol-based with silicone fluids.
  • Clear vinyl tubing sized to fit bleed nipples
  • Small catch bottle for old fluid
  • Wrench for bleed nipples (usually 8mm or 10mm) and a small box wrench for master cylinder cap
  • Turkey baster or hand vacuum pump (optional) for removing fluid from the master cylinder
  • Shop rags and brake cleaner
  • Disposable gloves, eye protection
  • Torque wrench (for reassembly where applicable)

Model notes specific to the 2000 BigBear 400

  • The 2000 BigBear is a simple, non-ABS ATV hydraulic brake system with separate front and rear master/reservoirs or a single combined master depending on factory options. Inspect your machine to confirm layout before starting.
  • Reservoirs are small and can be easily overfilled; work slowly and top up only as needed to avoid spillage.
  • Brake lines on older ATVs may show wear or corrosion at fittings. If rubber lines feel brittle or show cracking, replace them rather than just bleeding.
  • Paint and plastics on the BigBear are vulnerable to brake fluid. Protect surfaces and wipe any spills immediately with brake cleaner and a rag.

Preparation

  • Park on level ground, shift into park/neutral, and secure the machine so it cannot roll. Remove ignition key.
  • Clean around reservoirs and calipers to avoid contamination entering the system when you open caps or nipples.
  • Open the master cylinder reservoir cap(s). If the fluid level is low, note current fluid color (dark = needs change). Use a turkey baster to remove most old fluid if you plan to do a full flush before bleeding.
  • Top the reservoir to the specified level with new fluid. Keep the reservoir cap loosely in place to reduce contamination while working.

Basic two-person bleed method (recommended)

  1. Start at the bleed nipple farthest from the master cylinder (usually a rear caliper then front caliper sequence). For single-circuit ATVs, follow the factory sequence if known; otherwise use farthest-to-closest logic.
  2. Attach clear tubing to the bleed nipple and place the other end into a catch bottle partially filled with a little new fluid to prevent air re-entry.
  3. Have your helper depress the brake lever or pedal firmly and hold it down.
  4. With the lever held, open the bleed nipple one-quarter to one-half turn until fluid and air bubbles flow into the tube. Close the nipple before the helper releases the lever to avoid drawing air back in.
  5. Repeat: pump & hold, crack nipple, close nipple, release lever. Continue until only clear new fluid (no bubbles) flows and the lever feel is firm.
  6. Top up the reservoir frequently during the process. Never allow the reservoir to run dry or you will reintroduce air into the system.
  7. Once the caliper is clear, tighten the bleed nipple to spec (hand tight plus a small snugavoid over-torquing). Wipe any spilled fluid and move to the next wheel.

Single-person methods (vacuum or pressure)

  • Vacuum pump: attach pump hose to bleed nipple, open nipple, and draw fluid through while topping the master reservoir. Continue until clear fluid appears. Close nipple before disconnecting.
  • Pressure bleeder: pressurize reservoir per tool instructions, open each bleed nipple in sequence until clear fluid flows. Monitor reservoir level and pressure.

Full fluid replacement (flush) recommendation

  • If fluid is very dark, perform a full flush: remove as much old fluid from the reservoir as possible, refill with new fluid, then bleed each caliper until the expelled fluid is the same color as the new fluid and no air appears.
  • Some owners prefer repeating the flush cycle twice for a very old system to ensure contaminants are removed.

Final checks

  • Verify all nipples and reservoir caps are sealed and clean.
  • Operate the brake lever/pedal several times with the machine off to confirm a firm feel. If spongy, re-bleed the system.
  • Test ride at low speed in a safe area to confirm braking performance before returning to normal use.
  • Dispose of old brake fluid responsibly; do not pour down drains.

Torque & safety reminders

  • Tighten bleed nipples snuglydo not over-torque. If you have a torque spec from the service manual, use it.
  • Avoid getting brake fluid on painted surfaces or plastic components; it removes finish immediately. Rinse and clean spills right away.
  • If calipers, master cylinder, or lines show leaks or damage during inspection, replace parts rather than relying on bleeding alone.

Maintenance intervals & tips

  • Change brake fluid every 1-2 years or sooner if fluid darkens. Water absorption and contamination reduce braking performance and can corrode internal parts.
  • Store spare fluid sealed and in a cool, dry place. Discard any opened bottle after several months to avoid moisture uptake.
  • Keep a small brake repair kit and replacement bleed nipple washers with your tool kit for trail repairs.

Following this MotoSport procedure will help you replace and bleed the brakes on your 2000 Yamaha BigBear 400 4x4 reliably. If you encounter persistent sponginess, visible damage, or uncertainty about system layout on your particular MMY machine, contact a qualified ATV technician.

Related Shopping Categories

Shop Brake Fluid for a 2000 YAMAHA BIGBEAR400 ATV.

Shop Brake Bleeders for a 2000 YAMAHA BIGBEAR400 ATV.

Shop Brake Pads for a 2000 YAMAHA BIGBEAR400 ATV.

Shop Brake Lines for a 2000 YAMAHA BIGBEAR400 ATV.

Shop Brake Tools for a 2000 YAMAHA BIGBEAR400 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.