How to Bleed and Replace Brake Fluid on a 1986 Honda TRX350 4X4
Shop parts for a 1986 Honda TRX350 ATV.
This MotoSport guide walks you through safely flushing and bleeding the brake system on a 1986 Honda TRX350 4X4. The directions cover front disc calipers and the rear drum brake system on this model year, plus model-specific notes owners should know before starting.
What you need
- Brake fluid: DOT 3 (Honda recommends DOT 3; DOT 4 is compatible but do not mix with mineral oils)
- Clear 1/4" vinyl tubing
- Catch bottle and a small amount of brake fluid in the bottle to prevent air backflow
- Wrench to fit bleed nipples (typically 8mm or 10mm)
- Box-end wrench for banjo bolt if replacing hoses (commonly 12mm)
- Vacuum bleeder or syringe (optional but speeds the job)
- Clean rags, rubber gloves, safety glasses
- Torque wrench (for reassembly and banjo bolt crush washers)
- New crush washers for banjo bolts and replacement rubber brake hoses if aged
Safety and prep
- Work on a level surface; block wheels and set ignition off.
- Brake fluid will damage paint & plastics — protect bodywork and immediately wipe spills.
- Wear gloves and eye protection. Dispose of old fluid according to local hazardous-waste rules.
- Inspect master cylinder reservoir for cracking or clouding — this tank can become brittle on older TRX350s.
Model-specific notes for the 1986 TRX350 4X4
- The 1986 TRX350 typically uses front disc calipers and a rear drum. The system runs from a single master cylinder; bleeding order and complete flushing are important to avoid leftover contamination.
- Rubber hoses and the small rubber reservoir on the master cylinder are known to harden and crack on older machines. Replace any hose or reservoir that looks brittle.
- Banjo bolts on the TRX often use crush washers; always replace washers when loosening the hydraulic fittings to ensure a leak-free seal.
- If brakes feel spongy after bleeding, check caliper pistons for corrosion and the rear wheel cylinder (drum) for leaks or seized pistons — both are common failure points on restored or high-hour ATVs.
Step-by-step: Flush and replace brake fluid
General bleed order: start at the wheel farthest from the master cylinder and finish with the closest. For the TRX350 that typically means: right front → left front → rear drum. If your routing differs, confirm which wheel is farthest from the master cylinder and follow that sequence.
- Remove reservoir cap and diaphragm. Siphon or absorb most old fluid out of the master reservoir but leave a small amount to keep the system wet. Top up with fresh DOT 3 fluid.
- Raise the ATV so wheels are off the ground and supported safely. Remove wheels as needed for access.
- Attach clear tubing to the bleed nipple on the wheel you will start with; submerge the other end in a small catch bottle containing a little fresh fluid to prevent drawing air back in.
- Loosen the bleed nipple a quarter turn. Have an assistant slowly depress the brake lever/pedal until firm, then hold pressure. While holding, open the nipple briefly to allow fluid and air to flow into the hose, then close the nipple before the lever/pedal is released. Repeat until clear fluid with no bubbles emerges.
- After each cycle, top the master reservoir to prevent it from running dry. Do not let the reservoir fluid level drop below the minimum or air will re-enter the system.
- Work through each wheel in the correct order. For the rear drum, access the wheel cylinder bleed screw behind the drum or backing plate. The same open/close while held pressure method applies. If the drum cylinder is difficult to access, use a vacuum bleeder on the bleed screw.
- If you prefer one-person methods: use a vacuum bleeder on each bleed nipple while an assistant pumps the brake or while you gently operate the lever. Alternatively, use the pump-and-hold method described above if no vacuum tool is available.
- When all wheels are bled and the fluid runs clear with no air, close all bleed nipples and tighten to a snug torque; check factory specs if available — tighten securely but avoid rounding fittings. Reinstall new crush washers on banjo bolts if disturbed and torque to spec.
- Top off the master reservoir to the proper level, reinstall the diaphragm and cap. Pump the brake lever/pedal several times to confirm a firm feel before riding.
- Check for leaks around bleed nipples, banjo bolts, hose fittings, calipers and wheel cylinder. Recheck fluid level after a short test ride and adjust as necessary.
Common issues and fixes for the TRX350
- Persistent spongy brake feel after bleeding: re-bleed using vacuum or pressure bleed until no bubbles appear; inspect for collapsed hoses or internal master-cylinder leaks.
- Sticky calipers or seized wheel cylinder pistons: remove, clean, and rebuild calipers/wheel cylinder or replace with rebuilt units. Corroded pistons are common on aged ATVs.
- Cracked reservoir or brittle rubber pieces: replace the reservoir, cap and any aged rubber hoses. Parts can be scarce for older MMY so inspect ahead and have replacements ready.
Maintenance tips
- Replace brake fluid every 1-2 years or sooner if contaminated. Regular flushing prevents moisture buildup and corrosion in the system.
- Keep a small spare supply of DOT 3 in a sealed container; brake fluid absorbs moisture quickly once opened.
- After any brake service, perform a thorough roadside/brake check at low speed before returning to normal riding.
Follow these steps and your 1986 Honda TRX350 4X4 will have reliable brake performance. If you need parts, accessories or replacement rubber hoses for this MMY, visit the MotoSport parts catalog linked above to find model-specific items.
Related Shopping Categories
Shop Brake Fluid for a 1986 Honda TRX350 ATV.
Shop Brake Bleeders for a 1986 Honda TRX350 ATV.
Shop Brake Pads for a 1986 Honda TRX350 ATV.
Shop Brake Lines for a 1986 Honda TRX350 ATV.
Shop Brake Tools for a 1986 Honda TRX350 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.
