How to Bleed & Replace Brake Fluid on a 1993 Yamaha YFM350ER MOTO-4

Shop parts for a 1993 Yamaha YFM350ER MOTO-4 ATV.

Overview & safety

This guide is proprietary to MotoSport and covers complete replacement of brake fluid and a thorough bleed on a 1993 Yamaha YFM350ER MOTO-4. Work on a cool machine, outdoors or in a well-ventilated area, on level ground, with the engine off and key removed. Wear eye protection and gloves. Brake fluid damages painted surfaces – clean spills immediately with water and protect finish with rags or tape.

What you’ll need

  • Correct brake fluid (check reservoir cap marking; commonly DOT 3 or DOT 4). Use only the specification marked on the reservoir.
  • Clear tubing sized to bleed nipple
  • Catch bottle for old fluid
  • Open-end wrench for bleed nipples (usually 8mm or 10mm)
  • Brake bleeder kit, vacuum pump, or a help from an assistant
  • Clean rags, small funnel, and a syringe or turkey baster (for removing old fluid)
  • Torque wrench for caliper/hose fasteners if reinstalling hardware

Model-specific notes for the 1993 YFM350ER

  • The YFM350ER MOTO-4 is an early 350cc ATV with hydraulic disc brakes front (dual) and a hydraulic rear brake. Confirm your machine’s layout visually before beginning.
  • Reservoirs are small — don’t let the master cylinder run dry during bleeding. Running dry can introduce air and require extra bleeding time.
  • Original fittings can be corroded from age. Apply penetrating lube to seized bleeder nipples and avoid rounding nut flats by using the correct wrench size.
  • If caliper pistons are sticky or seized due to age, bleeding will not fully restore feel. Inspect calipers, pads, and lines while replacing fluid.

Step-by-step: full brake fluid change and bleed

Perform these steps for each circuit: front left, front right, rear — following the bleed order farthest from the master cylinder first and nearest last. If unsure which is farthest, do rear first, then passenger-side front, then driver-side front.

  1. Raise and secure the ATV so wheels can turn freely. Remove wheel(s) only if needed to access bleed nipples and calipers.
  2. Clean the master cylinder cap area. Remove cap and diaphragm slowly to avoid splashing. Siphon out as much old fluid as possible from the reservoir with a syringe or turkey baster.
  3. Refill reservoir with fresh brake fluid to the full line. Keep the cap off but covered with a clean rag while bleeding to avoid contamination and to allow air to escape.
  4. Attach clear tubing to the bleed nipple of the first caliper. Put the other end into a catch bottle partially filled with fresh fluid so the nipple stays submerged and no air is drawn back in.
  5. Have an assistant slowly depress the brake lever/pedal several times and hold it on the last stroke. Open the bleed nipple about a quarter turn to allow fluid and air to escape. Close nipple before the assistant releases the lever/pedal. Repeat until no bubbles appear in the tubing and fluid is clear.
  6. After each cycle, top off the master cylinder to prevent it from running dry. Repeat the process for each brake caliper in the chosen order.
  7. If you prefer a one-person method, use a vacuum bleeder or a pressure bleeder: attach the tool to the bleed nipple or reservoir and draw/pressurize fluid through until clear. Follow tool instructions and maintain reservoir level.
  8. When lines are bubble-free, tighten bleed nipples to manufacturer snugness. Wipe away spilled fluid and replace reservoir diaphragm and cap. Pump the brake lever/pedal slowly to confirm firm feel and correct travel. If soft or spongy, repeat bleeding.
  9. Lower the ATV, torque wheel fasteners to spec if removed, and road-test at low speed in a safe area to confirm braking performance.
  10. Properly dispose of used brake fluid per local regulations.

Common problems & troubleshooting

  • Persistent spongy lever: suspect trapped air, a leak, collapsed hose, or contaminated master cylinder. Recheck connections and hose condition; inspect master cylinder for internal leaks.
  • No fluid flow from a caliper: stuck piston or blocked passage. Remove caliper, inspect and free piston or service caliper as needed.
  • Leaking bleeder nipple or line: replace the nipple or hose and repeat full bleeding.
  • Paint damage from spilled fluid: neutralize with water immediately and re-clean the area; if damaged, plan to touch up finish.

Maintenance recommendations

  • Replace brake fluid every 1-2 years or sooner if it looks dark or contaminated.
  • Inspect brake lines, hoses, pads, and calipers at each fluid change. Replace rubber hoses older than 10-15 years or showing cracking.
  • Keep a small bottle of the correct brake fluid on hand for topping off during long riding seasons.

Final checks

Confirm there are no leaks, brake lever/pedal feel is firm, and stopping performance is consistent. If you encounter persistent problems after bleeding, have the master cylinder, calipers, and lines inspected and rebuilt or replaced as necessary.

Related Shopping Categories

Shop Brake Fluid for a 1993 Yamaha YFM350ER MOTO-4 ATV.

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Shop Brake Lines for a 1993 Yamaha YFM350ER MOTO-4 ATV.

Shop Brake Tools for a 1993 Yamaha YFM350ER MOTO-4 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.