How to Change the Oil in a 2023 KTM 125 SX: A MotoSport.com Exclusive Guide

Shop parts for a 2023 KTM 125 SX Dirt Bike.

Regular oil changes are essential for keeping your 2023 KTM 125 SX running at peak performance. This dirt bike features KTM’s new-generation engine design, and while the process is consistent across all new TBI two-stroke models, there are some key steps and torque specs unique to this motorcycle. Use this step-by-step guide, proprietary to MotoSport.com, to change your oil confidently and safely.

Tools and Supplies Needed

  • 8mm wrench or socket (for drain bolt)
  • Torque wrench (capable of measuring in Newton-meters)
  • Oil drain pan
  • New crush washer/seal for drain bolt (recommended)
  • Funnel
  • Measuring cup (metric, for oil volume)
  • Gloves and rags (for cleanliness)
  • Engine oil (15W-50)

Model-Specific Call-Outs: KTM 125 SX (2023)

  • This oil change procedure also applies to the 2023 125 XC, 250 SX, 250 XC, 300 SX, and 300 XC due to shared engine architecture and design.
  • KTM specifies 800 milliliters (0.8 liters or 0.85 quarts) of Gear Oil 15W-50.
  • Tighten the drain plug to 20 Nm (Newton-meters), as conveniently stamped on the side of the engine case for reference.
  • The oil level check is performed by removing the level screw—add oil until it gently seeps from this hole.
  • This model uses a magnetized drain plug; check for and remove any metallic debris before re-installing.

Step-by-Step Process

  1. Warm Up the Engine
    • Run your bike for about three minutes to warm the oil slightly. This helps suspend contaminants and allows the oil to drain quickly and completely.
  2. Stabilize the Bike
    • Place the KTM 125 SX on a flat surface and secure it using a stand for stability during the process.
  3. Remove the Skid Plate (if installed)
    • Most MX applications require this for cleaner access to the drain bolt below the engine.
  4. Locate and Remove the Drain Plug
    • The drain plug is located on the bottom of the crankcase. Use your 8mm wrench or socket, position the oil drain pan directly underneath, and loosen the bolt, allowing old oil to empty completely into the pan.
    • Let the bike drain for several minutes to ensure thorough evacuation of old oil.
  5. Inspect and Clean the Drain Plug
    • The 2023 KTM 125 SX drain plug is magnetic. Wipe away any metallic particles or sludge attached to the magnet, as this helps monitor engine condition and protects moving parts.
    • Install a new crush washer/seal to prevent leaks.
  6. Replace and Torque the Drain Plug
    • Thread the drain plug by hand until snug.
    • Using a torque wrench, tighten the plug precisely to 20 Nm. This is critical—overtightening can strip threads, while undertightening can lead to leaks.
  7. Remove the Filler Cap and Level Check Screw
    • The filler cap (with O-ring) is typically located on top or the side of the engine case. The oil level check screw is usually found on the right-side cover. Remove both.
  8. Add New Oil
    • Using the funnel, pour in fresh 15W-50 engine oil slowly. Most new KTM 125 SX engines require exactly 800 ml.
    • Add oil until it begins to gently seep from the level check screw opening. This ensures the correct fill level and prevents overfilling.
  9. Reinstall All Plugs and Caps
    • Once oil seeps from the level screw, reinstall and tighten the screw.
    • Replace the oil filler cap, ensuring the O-ring is intact and properly seated.
  10. Check for Leaks and Final Clean-Up
    • Start the engine and let it idle for a minute.
    • Inspect the drain and level screw areas for any signs of seepage or leaks.
    • Wipe down any excess oil, and properly dispose of the used oil in accordance with local regulations.

Tips and Warnings for 2023 KTM 125 SX Owners

  • Always use a quality oil that meets or exceeds KTM’s recommendations to preserve clutch and gearbox longevity.
  • Changing oil more frequently (after every few rides or every 5–10 engine hours in racing conditions) ensures peak performance and durability.
  • Consult your owner’s manual for specific part numbers and additional recommendations—routinely check for updated specs or recalls.
  • Avoid pressure washing engine areas directly after an oil change to prevent water intrusion into open components.

By following these steps and paying attention to the unique requirements of your 2023 KTM 125 SX, you’ll keep your dirt bike performing at its best, race after race.
For all parts, tools, and factory-approved lubricants, trust MotoSport.com—your destination for all things dirt bike.

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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.