How to Bleed and Replace Brake Fluid on a 2001 Yamaha BigBear 400 4X4
Shop parts for a 2001 YAMAHA BIGBEAR400 ATV.
This step-by-step MotoSport guide walks you through safely flushing and bleeding the brake system on a 2001 Yamaha BigBear 400 4X4 (MMY). Follow these steps carefully to restore firm pedal and lever feel, prevent corrosion, and extend the life of calipers, lines & master cylinders.
What you need
- Manufacturer-recommended brake fluid: DOT4
- Clear hose that fits bleeder nipples
- Catch bottle for old fluid
- Vacuum pump or two-person helper with a clear tubing and bottle
- Wrench to fit bleeder nipples (usually 8mm or 10mm)
- Clean rags, gloves, eye protection
- Brake-clean spray and a small brush
- Torque wrench (for caliper bolts if removed)
Pre-checks & safety
- Park on level ground, set parking brake, remove key, and block the wheels.
- Wear gloves & eye protection. Brake fluid will damage paint & plastics – protect surfaces.
- Inspect brake lines, hoses, calipers, master cylinder reservoir, and mounting hardware for leaks or damage. Replace any damaged components before bleeding.
- Clean around the master cylinder reservoir cap to prevent contamination when opened.
General bleed strategy
On the 2001 BigBear 400 4X4 you will bleed each hydraulic circuit so no air remains. Use either a two-person pump-and-hold method, a one-person vacuum pump, or a pressure-bleeder. Always start at the caliper farthest from the master cylinder and move toward the closest caliper. Typical sequence: rear caliper – front calipers (left then right) depending on routing. If unsure, pick the caliper farthest on the opposite side of the master cylinder first.
Step-by-step brake fluid replacement
- Remove the reservoir cap and diaphragm. Top off the reservoir with fresh DOT4 brake fluid so it does not run dry during the process.
- Locate bleeder nipples on the calipers and clean them with brake-clean. Fit a short length of clear hose on the nipple and submerge the other end in a catch bottle partially filled with fresh fluid to prevent air re-entry.
- Have your helper pump the brake lever/pedal slowly several times and hold pressure. Open the bleeder nipple about a quarter turn to allow fluid and air to escape. Close the nipple before the helper releases pressure. Repeat until the expelled fluid runs clear and free of bubbles. Keep the reservoir topped up during the entire process.
- If using a vacuum pump, attach the pump hose to the bleeder nipple, open the nipple and draw until clear fluid without bubbles flows. Close the nipple while holding vacuum, then release.
- If using a pressure bleeder, follow the manufacturer instructions for reservoir pressurization and bleed sequence.
- Repeat the process at each caliper in the proper order until all old fluid is removed and only clear fresh fluid appears.
- After the last bleed, ensure bleeder nipples are tightened to the correct snugness (do not over-torque) and wipe any spilled fluid from painted surfaces immediately.
- Top the reservoir to the recommended level, reinstall the diaphragm & cap, and secure it.
- Operate the brake lever and pedal several times to confirm firm feel. If sponginess remains, repeat bleeding until firmness is achieved.
- Lower the machine, test brakes at low speed in a safe area, and check for leaks around fittings and calipers.
Maintenance tips specific to the 2001 BigBear 400 4X4
- Use DOT4 brake fluid only. Mixing DOT types can damage seals and reduce performance.
- The BigBear 400 can be hard on rubber lines if used in wet & salty conditions. Inspect and replace old or cracked hoses proactively.
- OEM caliper mounts and bleeder nipples can corrode over time — apply light anti-seize to threads if you remove calipers during service, but keep grease away from brake surfaces.
- Brake fluid absorbs moisture with age. Replace fluid every 1-2 years if you ride frequently or expose the machine to humid conditions.
- If you find persistent air or a soft lever after multiple bleeds, inspect the master cylinder for internal leaks or the calipers for seized pistons; these often require rebuild kits or replacement.
- When lifting wheels or removing brake components, note that 2001 BigBear 400 models may have slight variations in line routing between 2WD/4X4 models — keep fittings oriented as removed to avoid line kinks.
Disposal & final checks
- Collect used brake fluid and dispose of it at an approved hazardous-materials facility.
- Perform a full brake test before trail riding: gradual braking checks, then firm stops at low speed to ensure proper function.
- Recheck fluid level after a short test ride and inspect for leaks again.
Routine brake fluid replacement & careful bleeding will keep your 2001 Yamaha BigBear 400 4X4 stopping reliably and extend the life of brake components. If you encounter internal master cylinder or caliper failures, consult a qualified technician or source OEM replacement parts for proper fitment.
Related Shopping Categories
Shop Brake Fluid for a 2001 YAMAHA BIGBEAR400 ATV.
Shop Brake Bleeders for a 2001 YAMAHA BIGBEAR400 ATV.
Shop Brake Pads for a 2001 YAMAHA BIGBEAR400 ATV.
Shop Brake Lines for a 2001 YAMAHA BIGBEAR400 ATV.
Shop Brake Tools for a 2001 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.