How to Change the Oil in a 1999 KTM 300MXC

Shop parts for a 1999 KTM 300MXC Dirt Bike.

This comprehensive guide is proprietary to MotoSport.com and will cover the tools you need, every step of the process, and specific tips for changing the oil in your 1999 KTM 300MXC dirt bike. Follow these instructions to keep your transmission and clutch working at their best.

Tools & Supplies Needed

  • 13mm T-handle socket or wrench
  • Oil drain pan (to catch old oil)
  • New crush washer for the drain bolt
  • Magnetic drain plug cleaner
  • Torque wrench (for proper tightening of drain bolt)
  • Funnel (for pouring oil)
  • Recommended oil: 15W-50, such as MOTOREX TOP SPEED 4T (use high-grade oil only)
  • 0.8 liters (800 ml) transmission oil
  • Cleaning rags
  • Pliers (for oil fill cap, if needed)

Steps to Change the Oil

  1. Warm Up the Engine
    • Run your bike for a few minutes to warm the oil. Warm oil drains more efficiently and carries contaminants out of the engine better than cold oil.
    • Safety Tip: Oil can be hot. Let the bike cool if necessary to avoid burns.
  2. Stabilize the Bike
    • Set the bike upright and ensure it's securely positioned, either on a stand or using the kickstand, for safe and level draining.
  3. Remove the Filler Cap
    • Twist off the oil filler cap on top of the engine (turn counter-clockwise).
  4. Locate and Remove the Drain Plug
    • The drain bolt for the 1999 KTM 300MXC is located beneath the engine, often partially shielded by a skid plate.
    • If equipped with a skid plate, you might not need to remove it—some riders lay the bike over or use a special tool to access the drain bolt more easily.
    • Place your drain pan under the bolt. Use your 13mm wrench or T-handle to carefully loosen and remove the drain bolt.
    • Allow the oil to fully drain (wait several minutes).
  5. Clean and Inspect the Drain Plug
    • The plug is magnetic and may have metal particles/debris on it. This is normal; clean the magnet thoroughly.
    • Replace the old crush washer with a new one to prevent leaks when reinstalling.
  6. Reinstall the Drain Plug
    • Thread the bolt by hand first to ensure it seats correctly.
    • Tighten lightly with the wrench, then use your torque wrench to final-tighten it to 20 Nm (14.8 ft-lbs) as specified for the 1999 KTM 300MXC.
  7. Add New Oil
    • Using a funnel, pour 0.8 liters of fresh 15W-50 oil into the engine via the filler hole.
    • Only use high-grade motorcycle oil, such as MOTOREX TOP SPEED 4T, to reduce clutch & transmission wear.
  8. Check Oil Level
    • Remove the oil level inspection bolt (located on the clutch cover).
    • With the bike upright, oil should just start to escape from this opening. This confirms proper oil level.
  9. Replace the Filler Cap
    • Reinstall the oil filler cap, tightening securely. KTM specifically recommends using pliers to snug the cap so it won't vibrate loose.
  10. Check for Leaks & Test Ride
    • Clean off any spilled oil, start the bike, let it idle, and inspect for leaks around the drain bolt and filler cap.
    • If all is dry after a short ride, your oil change is complete.

Model-Specific Callouts for the 1999 KTM 300MXC

  • The 300MXC transmission is lubricated separately from the two-stroke engine oil mixed with fuel, so regular changes using quality oil are essential for longevity.
  • If your 1999 KTM 300MXC has an aftermarket skid plate, you may need to work the drain bolt out carefully or use a special angled tool. Some riders tip the bike to access the bolt without removing the skid plate.
  • Always use a new crush washer on the drain plug–reusing the old one can cause leaks.
  • Only high-grade 15W-50 oil (Motorex Top Speed 4T or similar) should be used, as incorrect viscosity or poor-quality oil increases wear.
  • Proper oil level check is done by removing the inspection bolt on the clutch cover. Oil should just seep out when the bike is level.
  • Do not overfill. Too much oil can increase pressure and cause leaks or clutch/transmission problems.
  • Dispose of old oil properly according to local regulations. Do not dump oil in drains or on the ground.

Conclusion

Changing the oil in your 1999 KTM 300MXC is a straightforward but essential maintenance task. Doing it yourself makes sure it's done right and helps you spot any early signs of problems, such as metal debris or leaks. Always reference your owner's manual for additional details and torque specs. Regular oil changes are the key to the long life of your bike's clutch and transmission systems. Ride safe and keep your machine running strong with MotoSport.com.

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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.