How to Change the Oil in a 2016 Yamaha YZ125

Shop parts for a 2016 Yamaha YZ125 Dirt Bike.

Regular oil changes are crucial for keeping your 2016 Yamaha YZ125 running at peak performance. While the YZ125 uses a premix for its two-stroke engine lubrication, you still need to change the transmission (gear) oil regularly to ensure smooth shifting and to protect internal components. Follow this guide for a step-by-step, model-specific process, including the tools required and expert tips for your YZ125.

Tools and Materials Needed

  • 12mm socket/ratchet – for drain bolt
  • 4mm Allen wrench – for oil check bolt
  • Drain pan
  • Long funnel – to navigate the fill location under the exhaust
  • Measuring cup – for precise oil measurement
  • Clean rag
  • New transmission oil – recommended: 10W-40 motorcycle-specific oil with wet clutch protection (Valvoline 10W-40 or Yamalube recommended)
  • Replacement crush washer (for drain bolt, optional but recommended)

Preparation

  • Ensure the bike is on level ground and secure, preferably on a stand.
  • Start the engine and let it idle for a few minutes to warm up. This helps the oil drain more completely by reducing viscosity.

Step-by-Step Oil Change Process

  1. Locate the Drain Bolt:
    • The drain bolt for the transmission oil is located under the crankcase on the bottom left side of the engine. It uses a 12mm socket to remove.
  2. Drain the Old Oil:
    • Place your drain pan directly beneath the drain bolt.
    • Use the 12mm socket/ratchet to remove the drain bolt.
    • Allow oil to fully drain—this may take several minutes if the engine was warmed up.
    • Inspect the crush washer for wear; replace it if it appears flattened or damaged.
  3. Reinstall the Drain Bolt:
    • Reinstall the drain bolt with the (optional) new washer. Torque the drain bolt to 14 ft-lbs (do not overtighten as this could strip the threads).
  4. Add New Oil:
    • Remove the oil fill cap, which is tucked beneath the exhaust pipe—the location will require a long funnel for easy pouring.
    • Measure 0.69 US quarts (660 mL) of your chosen oil using a measuring cup.
    • Slowly pour the oil into the fill port to avoid spills.
  5. Check the Oil Level:
    • The YZ125 has a check bolt (with a 4mm Allen wrench) on the right side of the engine. After adding oil, remove this check bolt.
    • If oil begins to slightly overflow from the check bolt opening, the oil level is correct.
    • If not, add small increments of oil until you see it begin to flow out gently.
    • Wipe away any excess and reinstall the check bolt.
  6. Reinstall the Fill Cap:
    • Tighten the fill cap securely, ensuring no debris enters the system.
  7. Clean Up:
    • Dispose of old oil responsibly at a recycling center or local auto shop that takes used oil.
    • Wipe any spilled oil from the bike to prevent dirt accumulation or fire hazards.

2016 Yamaha YZ125 Model-Specific Notes

  • The oil fill port is partially hidden underneath the exhaust header, making a long funnel or flexible spout essential to avoid spills.
  • Oil capacity is exactly 0.69 US quarts (660 mL) for an oil change.
  • Use only motorcycle-specific oil designed for wet clutches to ensure optimal clutch performance and durability.
  • Over-torquing the drain bolt can strip the aluminum threads—always use a torque wrench at 14 ft-lbs.
  • Replace the copper crush washer periodically to prevent leaks.
  • The gear oil should be checked and replaced every 5–10 hours of riding or after any muddy, wet, or particularly hard ride conditions.

Safety Reminders

  • Always change oil in a well-ventilated area. Be cautious, as the engine and oil may be hot after warming up.
  • Use gloves to minimize skin contact with used oil.
  • Double-check that all bolts and caps are properly reinstalled before starting the engine.

Final Thoughts

Routine transmission oil changes are the key to keeping your 2016 Yamaha YZ125 shifting smooth and lasting many seasons. Follow these steps and use quality oil, and you’ll ensure peak performance and protect your investment every ride. For more OEM parts, tools, and expert advice, visit MotoSport.com.

This guide was created exclusively for MotoSport.com and may not be reproduced without permission.

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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.