How to Bleed and Replace Brake Fluid on a 1990 Honda TRX300FW 4X4
Shop parts for a 1990 Honda TRX300FW 4X4 ATV.
This MotoSport guide gives a step-by-step, model-specific procedure for flushing and bleeding the hydraulic brakes on a 1990 Honda TRX300FW 4X4. Follow this procedure to remove contaminated fluid, restore pedal feel, and inspect brake hardware for wear. Work carefully, use compatible brake fluid, and follow all safety precautions.
What you need
- Brake fluid: DOT 3 or DOT 4 (use only one type; do not mix)
- Clear plastic tubing that fits bleed nipples
- Small clear catch bottle
- Turkey baster or fluid siphon
- Wrench set for bleed nipples and caliper/axle hardware
- Torque wrench (for final reassembly)
- Clean rags and parts cleaner
- Jack or ramps and wheel chocks
- Safety glasses and nitrile gloves
Notes specific to the 1990 TRX300FW 4X4
- The TRX300FW uses a conventional hydraulic brake system with a single master cylinder feeding front and rear circuits. Bleed nipples are located on the brake calipers (front) and on the rear brake caliper or wheel cylinder depending on the rear setup. Inspect each bleeder location before starting.
- Older TRX300FW rubber hoses and seals are prone to age cracking. If fluid is dark or you see swelling, replace hoses, seals, or the master cylinder before finishing the job.
- Park securely with the 4X4 engaged or the parking brake set so the transfer case does not allow wheel rotation during service. Chock non-lifted wheels.
- Brake fluid will damage paint and plastics. Keep rags handy and wipe spills immediately.
Prep and reservoir service
- Park on level ground, chock wheels, and remove seat or access panel to reach the master cylinder reservoir. Clean around the cap to prevent contamination when opened.
- Remove the cap and inspect the fluid: if dark, cloudy, or contains debris, a full flush is required. Use a turkey baster to remove most of the old fluid from the reservoir to minimize contamination of new fluid during the procedure.
- Top the reservoir with fresh DOT 3 or DOT 4 brake fluid only. Keep the cap loosely in place to minimize air entry while maintaining a vent.
Bleeding strategy
Bleed the system starting with the wheel or caliper farthest from the master cylinder and end with the closest. On TRX300-style layouts that means typically: rear (if it is the farthest), then front passenger side, then front driver side. If you are uncertain which is farthest from the master, trace the brake lines visually and follow the furthest-to-closest rule.
Step-by-step bleeding (one-person or two-person method)
- Raise the ATV so the wheels are off the ground and secure it on stands. Remove wheels if needed for access.
- Work on one bleed nipple at a time. Slip the clear tubing over the nipple and submerge the other end in the catch bottle partially filled with fresh fluid to prevent air re-entry.
- Have an assistant slowly pump the brake lever/pedal several times and hold it down. Open the bleeder 1/4 to 1/2 turn with the wrench so fluid flows into the tubing. Close the bleeder before the assistant releases the lever/pedal. Repeat until the discharged fluid runs clear and bubble-free. If working alone, use a one-way vacuum bleeder or a hand pump device and follow the manufacturer instructions.
- Keep the master cylinder reservoir topped up throughout. Never let it run dry or air will be introduced into the system and you will have to start over.
- Move to the next farthest wheel and repeat the process until all calipers/wheel cylinders have been bled and fluid runs clear from each bleed nipple.
- Once finished, tighten all bleeder screws to spec (snug, typically 7-12 lb-ft for many small caliper bleedersrefer to a repair manual if available), wipe off any spilled fluid, and refill the master cylinder to the proper level. Reinstall the cap and secure it.
Final checks and reassembly
- Torque caliper mounting bolts and any removed hardware to factory specifications where available. If you don't have the service manual, tighten carefully to a firm, safe setting and re-check after a short test ride.
- Bleed the parking brake or drum wheel cylinder if applicable using the same method.
- With the ATV still raised, apply the brake repeatedly to check for firm pedal/lever feel. If sponge or travel remains, re-bleedair is the cause.
- Lower the ATV and perform a slow, controlled test ride in a safe area to confirm braking performance before normal use.
Replacement intervals and additional maintenance tips
- Replace brake fluid every 1-2 years or sooner if it becomes dark or contaminated. Moisture absorption into brake fluid reduces boiling point and causes corrosion in the system.
- Inspect pads/shoes, rotors/drums, caliper pistons, and brake lines while bleeding. Replace worn pads/shoes and resurface or replace rotors/drums if scored or warped.
- When replacing any hydraulic component, bench-bleed the master cylinder before installing where possible to reduce trapped air.
- Keep a small amount of compatible brake fluid in your service kit for topping off after heavy use or track days.
Troubleshooting
- Soft pedal after bleeding: likely air in system or master cylinder internal leak. Re-bleed and inspect master cylinder seals.
- Leaking at a bleeder fitting: tighten and compress a small amount of thread seal if necessary, replace bleeder screw if damaged.
- Brake drag after bleeding: check caliper slide pins, piston return, and that bleed nipples are fully closed and not corroded.
Following this MotoSport-specific guide will get a 1990 Honda TRX300FW 4X4's brakes flushed and bled correctly while highlighting model-specific checks for aging components common to these ATVs. If you encounter persistent issues, consider having the brake system inspected by a professional technician.
Related Shopping Categories
Shop Brake Fluid for a 1990 Honda TRX300FW 4X4 ATV.
Shop Brake Bleeders for a 1990 Honda TRX300FW 4X4 ATV.
Shop Brake Pads for a 1990 Honda TRX300FW 4X4 ATV.
Shop Brake Lines for a 1990 Honda TRX300FW 4X4 ATV.
Shop Brake Tools for a 1990 Honda TRX300FW 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.
