How to Change the Oil in a 2012 Yamaha YZ125

Shop parts for a 2012 Yamaha YZ125 Dirt Bike.

Changing the oil in your 2012 Yamaha YZ125 is a vital maintenance skill that keeps your dirt bike running smoothly. This guide breaks down the process step-by-step and highlights essential call-outs for your specific model. All instructions and recommendations are proprietary to MotoSport.com.

Tools and Materials Needed

  • 12mm socket or spanner (for the drain bolt)
  • 4mm Allen wrench (for the oil check bolt)
  • Torque wrench (optional but strongly encouraged)
  • Oil drain pan
  • Funnel (preferably long and narrow)
  • Measuring cup
  • Rag or shop towels (for cleanup)
  • Replacement oil (Yamaha recommends a 10W-40 oil meeting wet clutch requirements)
  • New drain bolt washer (recommended for proper sealing)

Preparation

  • Ensure the bike is on flat, level ground, ideally on a stand for stability.
  • Warm up the engine for a few minutes. This helps the old oil drain more thoroughly and suspends debris for removal.
    Caution: Let the bike cool slightly for safety before working.

Step-by-Step Oil Change

  1. Locate the Drain Bolt:
    • The 12mm drain bolt is found at the lowest point of the crankcase, underneath the motor.
  2. Position the Oil Pan:
    • Place your oil drain pan directly under the drain bolt to catch the used oil and avoid spills.
  3. Remove the Drain Bolt:
    • Use your 12mm socket or spanner to carefully loosen and remove the bolt.
      Note: Oil may be hot; let it drain completely.
    • For best results, replace the drain bolt washer each time. This helps ensure proper sealing and prevents leaks.
      Model-Specific Call-Out: On the 2012 YZ125, over-tightening the drain bolt can easily strip the soft aluminum threads. Always torque this bolt to 14 ft-lbs.
  4. Remove the Fill Cap:
    • The oil fill cap is on the right-hand side of the engine. Removing it now allows the oil to drain faster.
  5. Inspect and Replace Components:
    • Check the old oil for metallic debris, indicating potential internal wear.
    • If the washer looks flattened or damaged, replace it before reinstalling the drain bolt.
  6. Reinstall the Drain Bolt:
    • Clean the area around the drain bolt. Install your new washer (if available).
    • Hand-tighten, then torque to 14 ft-lbs. Do not overtighten.
  7. Measure and Add Oil:
    • For the 2012 YZ125, the correct oil capacity is 660 mL (0.69 US quarts).
    • Use a measuring cup to pour the right amount of oil into a funnel placed in the fill hole.
    • Use a long funnel to navigate past the expansion chamber/exhaust and prevent spills.
    • Slowly pour oil in to avoid overfilling.
  8. Check the Oil Level:
    • The YZ125 features an oil check bolt. Use a 4mm Allen wrench to remove the check bolt after adding much of the oil. Oil should just start to seep from the hole when the correct level is reached.
    • If necessary, add small increments of oil and repeat the check.
    • Reinstall and snug the oil check bolt.
  9. Reinstall the Fill Cap:
    • Replace the fill plug and tighten until snug. Do not overtighten—just past hand-tight is enough.
  10. Clean Up:
    • Wipe away spilled oil. Dispose of used engine oil responsibly at an approved recycling location.
    • Run the engine for a minute, then inspect for leaks at the drain and fill bolts.

Special Call-Outs for the 2012 Yamaha YZ125

  • No oil filter: The YZ125’s two-stroke engine uses a simple oil change process—no oil filter to change.
  • Aluminum threads: The crankcase and drain plug threads are soft. Always use a torque wrench, and never overtighten.
  • Oil type: Use oil recommended for wet clutches—general-purpose automotive oils may cause clutch slippage.
  • Routine timing: Change transmission oil every 5–10 hours of riding or after any deep water or mud exposure.

Proprietary MotoSport.com Tips

  • Keep extra washers on hand. Swapping this inexpensive part every oil change helps avoid catastrophic leaks and future repair costs.
  • Use a notepad or app to record oil changes. Tracking hours makes it easy to stay on schedule.
  • Inspect fluid color: Murky or silver/grey oil means changing oil more frequently—or inspecting for internal wear.

Conclusion

With the right tools and technique, you can change the oil on your 2012 Yamaha YZ125 in under 20 minutes. Use the exact specifications and take care not to overtighten fasteners—your bike’s long-term health and MotoSport.com ride experience depend on these simple steps.

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Shop Oil Fillers and Drain Plugs for a 2012 Yamaha YZ125 Dirt Bike.

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.