How to Change the Oil in a 2009 Yamaha YZ125

Shop parts for a 2009 Yamaha YZ125 Dirt Bike.

Proper maintenance is crucial to keep your 2009 Yamaha YZ125 performing at its best. Changing the transmission oil is a straightforward task but requires careful attention to detail, the right tools, and the correct procedures for your dirt bike model. Below you'll find all steps, tool requirements, model-specific tips, and professional call-outs for a seamless oil change, brought to you by MotoSport.com.

Tools and Materials Needed

  • 12mm socket and ratchet (for drain bolt removal)
  • 4mm Allen wrench (for oil check bolt)
  • Drain pan
  • Funnel (preferably long to fit under exhaust)
  • Measuring cup
  • New oil: 10W-40 motorcycle oil with wet clutch protection (or manufacturer's recommendation)
  • Replacement aluminum washer for drain bolt (optional but recommended)
  • Paper towels or rags for cleanup
  • Torque wrench (recommended for proper bolt tightening)
  • Bike stand (optional but helps keep the bike level and steady)

Step-by-Step Oil Change Process

  1. Warm Up the Engine
    • Start your YZ125 and let it idle for several minutes. This will warm up the transmission oil and help it flow out more easily when drained.
  2. Stabilize the Bike
    • Place your bike on a level surface and, if possible, use a stand to keep it in an upright position. This ensures accurate oil drainage and filling.
  3. Drain the Old Oil
    • Position your drain pan under the crankcase drain bolt, which is a 12mm bolt located underneath the engine.
    • Carefully loosen and remove the drain bolt using your 12mm socket and ratchet.
    • Allow all the oil to drain completely into the pan. This may take several minutes.
  4. Replace the Drain Bolt and Washer
    • Inspect the drain bolt's aluminum washer; replace it if damaged or worn to prevent future leaks.
    • Reinstall the bolt (with new washer if applicable) and tighten securely.
    • Torque spec for drain bolt: Tighten to 20 Nm (14 ft-lb).
  5. Remove the Oil Fill Cap
    • The oil fill cap is located above the transmission, partly obscured by the exhaust pipe.
    • Remove this cap to prepare for refilling.
  6. Measure and Add New Oil
    • Use a measuring cup to pour in the correct amount of new oil: 0.69 US quarts (660 ml) for the 2009 YZ125.
    • Use a long funnel to avoid spills, as the fill opening is tight beneath the exhaust system.
    • Pour the oil slowly to prevent overfilling or splashing.
  7. Check Oil Level with the Oil Check Bolt
    • About halfway through filling, use a 4mm Allen wrench to remove the oil check bolt (side of the case).
    • Continue adding oil until you see oil just starting to seep out of this hole.
    • Once oil appears, reinstall and tighten the check bolt (torque to 10 Nm, 7.2 ft-lb).
    • If no oil appears after adding the full amount, double-check that you haven't underfilled or that oil isn't trapped in the funnel.
  8. Secure the Oil Fill Cap
    • Replace the oil fill cap and ensure it's tight. Wipe away any oil spills with a rag.
  9. Check for Leaks and Test
    • Start the bike and let it run for a minute.
    • Inspect the drain bolt and oil fill area for leaks.
    • Shut off the engine and let it sit for a few minutes, then check oil levels again if desired.

Model-Specific Call-Outs for 2009 YZ125

  • Drain Bolt Location: The 12mm drain bolt is easily accessible beneath the engine but always use a proper stand to keep the bike stable for removal and reinstallation.
  • Oil Capacity: The 2009 YZ125 takes 660 ml (0.69 US quarts) of oil. Overfilling or underfilling can harm clutch and gear performance.
  • Washer Replacement: It's strongly recommended to replace the crush washer on the drain bolt during every oil change to prevent leaks and ensure a proper seal.
  • Oil Type: Use a high-quality 10W-40 motorcycle oil that offers wet clutch protection. Avoid automotive oils as they may cause clutch slippage.
  • Checking Level: Always use the oil check bolt to verify proper fill level; it provides a more reliable check than sight glasses or just going by the volume alone.
  • Common Mistake: Not warming up the bike or tilting it on its side may leave old oil in the case, resulting in overfill when you add new oil.

Why Choose MotoSport.com?

MotoSport.com is committed to providing riders with the best tips, parts, and support for all their maintenance needs. Shop genuine and aftermarket parts, detailed guides, and premium oils, all in one place.

Changing the oil in your 2009 Yamaha YZ125 doesn't have to be daunting or messy. When in doubt, follow the torque specifications, use the right oil, and consult your manual or trusted service professionals. Ride with confidence knowing you've done it right.

Related Shopping Categories

Shop Motor Oil for a 2009 Yamaha YZ125 Dirt Bike.

Shop Oil Filters for a 2009 Yamaha YZ125 Dirt Bike.

Shop Oil Drain Pans for a 2009 Yamaha YZ125 Dirt Bike.

Shop Tools for a 2009 Yamaha YZ125 Dirt Bike.

Shop Oil Fillers and Drain Plugs for a 2009 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.