How to Bleed and Replace Brake Fluid on a 1987 Yamaha YFM350ER Moto-4
Shop parts for a 1987 YAMAHA YFM350ER ATV.
This service guide is proprietary to MotoSport and written specifically for owners of the 1987 Yamaha YFM350ER (Moto-4). It covers tools, safety, and a step-by-step procedure to replace and properly bleed the brake fluid in both front and rear hydraulic systems. Follow each step carefully & consult factory manuals for torque specs if needed.
Important model notes for the 1987 YFM350ER
- The YFM350ER uses a single hydraulic disc brake front and drum or disc depending on specific submodel — confirm whether your machine has rear drum or rear disc before buying parts.
- Brake components on the 1987 Moto-4 are older metallurgy; inspect master cylinder, caliper pistons, hoses & banjo fittings for corrosion, swelling, or pitting and replace if any signs of wear are present.
- Factory brake reservoirs are small; keep the reservoir topped while bleeding to avoid introducing air.
- The stock system is DOT 3/4 compatible. Confirm the correct DOT rating stamped on the reservoir cap before service. Never mix DOT 5 (silicone) with DOT 3/4 fluids.
- Replacement parts for older ATVs can be limited — inspect part numbers and hose lengths carefully when ordering.
Tools & supplies
- New brake fluid (DOT rating matching reservoir cap, typically DOT 3 or DOT 4)
- Clear plastic tubing that fits snug over bleeder nipples
- Catch bottle (preferably graduated) and a small clamp or a piece of wire to hold tubing tight
- Wrenches sized for bleeder nipples and banjo bolts (common: 8mm, 10mm)
- Screwdriver, clean rags, rubber gloves, eye protection
- Brake cleaner and a small brush for caliper/area cleaning
- Brake bleeder kit or vacuum pump (optional but helpful)
- Replacement crush washers for banjo bolts (recommended)
Safety first
- Work on a level surface with the engine off and key removed.
- Secure the ATV with wheel chocks and use jack stands if lifting.
- Brake fluid damages paint & plastics; immediately wipe spills and rinse with water if contact occurs.
- Wear gloves & eye protection. Dispose of used fluid per local regulations.
Preparation
- Clean the master cylinder reservoir cap area thoroughly to prevent contamination when opened.
- Remove the reservoir cap and diaphragm; cover opening lightly with a clean rag to limit debris entry.
- Inspect fluid color. Dark or contaminated fluid should be fully replaced.
- Remove wheels if needed for easier access to calipers or rear brake assembly.
Step-by-step: full fluid replacement & bleed
- Top reservoir with fresh brake fluid until near the max mark.
- Start with the brake circuit farthest from the master cylinder. On YFM350ER machines that use front brakes and a rear brake, begin with the right-front caliper, then left-front, then rear (or follow the manufacturer-specified order if stamped in service manual).
- Fit clear tubing over the bleeder nipple and route the other end into the catch bottle partially filled with fresh fluid to prevent air re-entry.
- Have an assistant slowly depress the brake lever/pedal and hold pressure. With pressure applied, open the bleeder nipple about a quarter turn until fluid and air bubble emerge; close nipple before assistant releases the lever/pedal. Repeat until no air bubbles appear and only clean fluid flows.
- Keep reservoir topped between cycles to avoid running the master cylinder dry; low reservoir will reintroduce air into the system.
- If stubborn air is present, use a one-way bleeder valve or vacuum pump on the bleeder nipple to draw fluid while watching the reservoir level. Alternatively, pressure-bleed from the reservoir (cap off and use a pressure bleeder) if available.
- For rear drum-equipped models: you may need to bleed the wheel cylinder(s). Remove the brake drum or access point, attach tubing to the bleeder, and pump slowly until clean fluid emerges. For cable-actuated parking brakes, ensure cable free play is correct after reassembly.
- Replace bleeder nipple dust caps and torque banjo bolts to proper spec using new crush washers when reinstalling any removed lines.
- Wipe all fittings clean, top reservoir to max, reinstall diaphragm and cap, and tighten securely.
- Test lever/pedal feel: lever should be firm, pedal should not sink. If spongy feeling remains, repeat bleeding sequence until firm.
- Perform a low-speed test ride in a safe area to confirm braking performance and check for leaks.
Tips & troubleshooting
- Spongy brake pedal after bleeding: check master cylinder seals and caliper pistons for wear. Internal master cylinder leaks can draw air and require rebuild or replacement.
- No fluid flow from bleeder: open bleeder slightly further but avoid rounding the nipple. Check for clogged passages & corrosion.
- If fluid turns dark shortly after service, inspect for moisture contamination in system components or source of contamination; flush again and replace damaged hoses.
- Always dispose of old brake fluid responsibly; do not pour it down drains or on the ground.
Post-service checks
- Inspect all connections for leaks after test ride.
- Re-check reservoir level and top if needed after a short break-in ride.
- Verify rear parking brake adjustment on models with mechanical park brake to ensure proper engagement.
- Record service date & mileage for future maintenance intervals.
For older YFM350ER machines, consider replacing rubber hoses and seals as preventive maintenance if they show age-related deterioration. Properly bled and maintained brakes are essential for safe trail riding.
Related Shopping Categories
Shop Brake Fluid for a 1987 YAMAHA YFM350ER ATV.
Shop Brake Bleeders for a 1987 YAMAHA YFM350ER ATV.
Shop Brake Pads for a 1987 YAMAHA YFM350ER ATV.
Shop Brake Lines for a 1987 YAMAHA YFM350ER ATV.
Shop Brake Tools for a 1987 YAMAHA YFM350ER 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.