How to bleed and replace brake fluid on a 2001 Yamaha Bigbear 400 2X4
Shop parts for a 2001 Yamaha Bigbear 400 2X4 ATV.
This MotoSport procedural guide walks you through flushing and bleeding the hydraulic brake system on a 2001 Yamaha Bigbear 400 2X4. Follow these steps carefully to restore firm lever/pedal feel, remove moisture and contaminants, and protect brake components.
Safety first
- Work on a level surface with the engine off, key removed and the parking brake engaged (if applicable).
- Wear safety glasses and nitrile gloves. Brake fluid is corrosive to paint and dries out rubber & plastic.
- Keep rags handy to immediately wipe any spilled fluid and protect painted surfaces with tape or plastic.
What you need
- Correct brake fluid as specified on the master cylinder cap (use the fluid recommended by Yamaha — check reservoir cap; most Yamaha ATVs use DOT 4 or DOT 3; never mix DOT 5 silicone with DOT 3/4).
- Clear plastic tubing that fits snugly over the bleed nipple.
- Catch bottle partly filled with fresh fluid to prevent air entry back into the system.
- Wrenches for bleed nipples and banjo bolts (use correct size and quality to avoid rounding).
- Assistant to operate the lever/pedal, or a one-person vacuum pump/syringe bleeder for single-operator use.
- Disposable funnel and small syringe or turkey baster for reservoir fluid changes.
- Rags and solvent-safe cleaner for cleaning parts and spills.
Model notes for the 2001 Yamaha Bigbear 400 2X4
- Reservoirs and hoses on older Bigbear models can become brittle from age and UV exposure – inspect closely before reusing. Replace any cracked reservoir, old hoses or swollen rubber lines to avoid leaks or future failure.
- The master cylinder cap will state the correct DOT rating – always follow that. If the cap is missing or unreadable, replace it before adding fluid.
- Banjo bolt copper crush washers are single-use hardware. Replace crush washers on banjo fittings whenever you open them to ensure a leak-free seal.
- There is no ABS to complicate bleeding, but caliper pistons can be sticky from sitting – if pistons don't move smoothly, rebuild or service calipers before bleeding.
- Check mounting bolts, caliper slide pins and pivot lubrication while the wheel is off. Rusted or seized hardware can mask braking issues.
Preparation & reservoir service
- Locate the brake master cylinder reservoir. Clean the exterior thoroughly so no dirt falls into the fluid.
- Remove the cap and diaphragm. If fluid is dark or contaminated, plan to fully replace it rather than topping up.
- Siphon or use a syringe to remove most fluid from the reservoir into a disposable container for proper disposal. Never reuse old fluid.
- Refill the reservoir with fresh recommended fluid to the full mark. Keep the cap off during the bleeding procedure but protect the opening from dirt and dust.
Standard two-person bleed method
- Position the ATV so you can access the bleed nipple on the caliper(s). Put the clear tube over the nipple and submerge the other end in the catch bottle with a small amount of fresh fluid to prevent air re-entry.
- Have an assistant slowly depress the brake lever or pedal several times and hold it to the stop.
- With the lever held down, open the bleed nipple about a half-turn until fluid & bubbles flow into the tube. Close the nipple before the assistant releases the lever. Repeat until no air bubbles appear when the lever is depressed and released.
- Top the reservoir frequently to keep it above the minimum level so air cannot be drawn into the master cylinder.
- Bleed each brake circuit in the correct sequence for your configuration. For a single front caliper and rear drum/disc, bleed the caliper(s) serving the lever first, then the rear. If both front and rear are hydraulic and separate circuits, follow the service manual sequence or bleed the most remote caliper first and finish with the closest.
One-person vacuum or syringe bleed
- Attach a vacuum pump to the bleed nipple or use a syringe at the reservoir to pull fluid through the system. Operate the vacuum while the lever is cycled slowly to help draw out bubbles.
- Keep the reservoir topped and monitor fluid clarity. Continue until clear fluid without air emerges.
Final steps and checks
- After bleeding, tighten the bleed nipple to the correct snugness — avoid overtightening. Wipe any fluid from fittings and painted areas immediately.
- Refill the reservoir to the full mark and reinstall the cap securely.
- Pump the lever/pedal several times to confirm firm feel. If it's spongy, repeat bleeding until elimination of air.
- Inspect for leaks around banjo bolts, bleed nipples and hoses. Replace crush washers or seals if any seepage is found.
- Test ride cautiously at low speed in a safe area to confirm braking performance before normal use.
Routine maintenance tips
- Replace brake fluid every 1-2 years or sooner if it becomes dark or contaminated. Moisture absorption reduces boiling point and braking performance.
- Replace rubber hoses every few years or on signs of cracking, swelling or soft spots. Rubber degrades faster with off-road use and exposure to elements.
- Keep an eye on pedal and lever free play — excessive travel can indicate worn linings, air in the system or master cylinder wear.
Troubleshooting
- Persistent spongy lever after thorough bleeding: suspect a leaking master cylinder or internal caliper seal issue; consider rebuild or replacement.
- Brake fade or poor performance after fluid change: confirm correct fluid type and that the system was properly bled; inspect pads/shoes and rotor/drum condition.
- Leaking around banjo bolts: replace copper crush washers and torque bolts evenly to seating value, then recheck for leaks.
Performing a full fluid replacement and careful bleed will keep your 2001 Yamaha Bigbear 400 2X4 stopping reliably. If you encounter component wear, brittle hoses, damaged reservoirs or stubborn caliper pistons, replace affected parts rather than risk a compromised brake system.
Related Shopping Categories
Shop Brake Fluid for a 2001 Yamaha Bigbear 400 2X4 ATV.
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Shop Brake Lines for a 2001 Yamaha Bigbear 400 2X4 ATV.
Shop Brake Tools for a 2001 Yamaha Bigbear 400 2X4 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.