How to Change the Oil in a 2016 KTM 125 SX — MotoSport.com Guide

Shop parts for a 2016 KTM 125 SX Dirt Bike.

Performing regular oil changes is crucial for extending the life and maintaining the performance of your 2016 KTM 125SX. This step-by-step guide will walk you through the entire process, listing all the tools you’ll need, including model-specific tips to make the job easier and more effective.

Tools and Materials Needed

  • 8mm and 10mm socket with ratchet (for drain and check bolts)
  • 19mm spanner or socket (for the oil filler cap)
  • Torque wrench (capable of 20 Nm / 14.8 ft-lbs)
  • Drain pan
  • Funnel
  • Clean rags or shop towels
  • New gear oil (refer to owner’s manual for type; generally 0.8 liters for this model)
  • New crush washer for the drain bolt
  • Pliers (for snugging the oil filler cap as per KTM’s suggestion)
  • Gloves (recommended for cleanliness and safety)

Preparation Steps

  • Start your bike and let it idle for a couple of minutes to warm up the oil. This helps it drain more completely, but be cautious as the engine and oil will be hot.
  • Make sure your bike is on a stable stand and turned off.
  • Gather all required tools and place the drain pan underneath the engine.

Step-by-Step Oil Change

  1. Remove the Oil Filler Cap
    Use your 19mm spanner or socket to loosen the oil filler cap. Removing this first helps the oil drain more freely by allowing air into the system. Set the cap aside in a clean area.
    KTM recommends snugging this cap down with pliers upon reinstallation to prevent it from coming loose unexpectedly.
  2. Loosen and Remove the Drain Plug
    Using your 10mm socket and ratchet, carefully remove the drain bolt located beneath the engine, right under the brake pedal area. Be ready for a quick flow of hot oil. Let the oil drain completely into the pan.
    “Be careful, the oil coming out could be very hot. Try not to drop your drain plug into the oil pan.”
  3. Clean and Inspect the Drain Plug
    Wipe down the drain plug with a clean towel. The KTM 125SX utilizes a magnetic drain plug — a small amount of metallic debris on it is considered normal. However, excessive shavings or chunks indicate internal wear and should be checked by a mechanic.
    “Having a little bit of debris on the magnet is not a big deal and completely normal.”
  4. Replace the Crush Washer
    Always fit a new crush washer on the drain bolt before reinstalling. This inexpensive step helps prevent leaks and is considered essential maintenance.
  5. Reinstall the Drain Plug
    Thread the plug in by hand to avoid cross-threading, then use your torque wrench to tighten it to 20 Nm (14.8 ft-lbs).
  6. Add New Oil
    Using a funnel, pour in the recommended gear oil for your KTM 125SX. For the 2016 model, the correct capacity is about 0.8 liters.
    “Refill the engine with 0.8 liters of oil.”
  7. Check Oil Level
    Unlike some bikes, KTM two-strokes use a check bolt to confirm correct oil level: continue adding oil until a small amount weeps out of this bolt. Once it stops running out but hasn’t stopped dripping entirely, reinstall the check bolt.
  8. Reinstall and Tighten the Filler Cap
    Screw on the oil filler cap and, per KTM’s recommendation, give it an extra snug with pliers. This prevents the cap from loosening due to vibration.
  9. Wipe Down the Engine and Check for Leaks
    Clean up any spilled oil with a rag and start the bike, letting it idle for a few moments. Turn it off and check for leaks around both the drain and filler caps.

Model-Specific Notes for the 2016 KTM 125 SX

  • Oil Capacity: 0.8 liters (double-check your manual to confirm the precise amount).
  • Crush washer replacement is required every oil change for a proper seal.
  • Magnetic drain plug must be cleaned every time. Metallic particles are normal, but excessive buildup is a red flag.
  • Check bolt method: Pour oil until it weeps from the check hole, then reinstall check bolt.
  • Snug filler cap with pliers (per KTM’s advice) to prevent unintentional backing off during rides.
  • If you have a skid plate installed, remove it for cleaner access to the drain plug.

Final Tips

  • Double-check the torque on your drain plug. Overtightening can strip threads; undertightening can cause leaks.
  • Only use manufacturer-recommended oil types and grades for the best engine life.
  • Dispose of old oil responsibly at an approved recycling center.

Following these steps will ensure your 2016 KTM 125 SX stays in peak condition. For all of your dirt bike maintenance needs, trust MotoSport.com — your source for parts, tools, and expert advice.

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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.