How to Change the Oil in a 2020 KTM 125SX: A MotoSport.com Step-by-Step Guide

Shop parts for a 2020 KTM 125SX Dirt Bike.

Regular oil changes are crucial for keeping your 2020 KTM 125SX performing at its best. Follow this detailed, model-specific guide to ensure a smooth and hassle-free oil change every time. This process applies specifically to the KTM 125SX 2020 two-stroke engine, and we've highlighted unique tips KTM owners should know.

Tools & Supplies Needed

  • 10mm socket and ratchet (for drain plug)
  • Torque wrench (for precise tightening, critical for KTM specs)
  • T-handle wrench (optional for ease)
  • New crush washer (for drain plug, prevents leaks)
  • Magnet cleaner or cloth (to clean magnetic drain plug)
  • Oil catch pan
  • Funnel
  • Pliers (for gently snugging oil fill cap)
  • KTM-recommended gear oil (check owner's manual; typically 0.8 liters for 125SX)
  • Gloves and rags (for safety and cleanup)

2020 KTM 125SX Oil Change Steps

  1. Warm Up the Engine
    Let your bike idle for a few minutes. Warm oil flows more easily, draining out more contaminants. Exercise caution—the oil may be hot.
  2. Access the Oil Drain Plug
    Place your bike on a stable stand. Slide the oil catch pan beneath the engine. Locate the oil drain plug underneath the right side, near the shift lever.
    Tip: Wearing gloves prevents burns and keeps hands clean.
  3. Remove the Oil Fill Cap
    Unscrew the oil fill cap on top of the engine. This allows air in so oil drains freely

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  4. Loosen and Remove the Drain Plug
    Using a 10mm socket, carefully loosen the drain plug. Allow the oil to drain completely. Avoid dropping the plug into the pan.
    • While oil drains, inspect and clean the magnetic drain plug—metal shavings are normal. Thoroughly wipe it off.
    • Replace the crush washer with a new one to prevent future leaks.
  5. Reinstall the Drain Plug
    Hand-thread the plug, then tighten lightly with the ratchet. Finish with a torque wrench, setting to 20 Nm (14.8 ft-lb), as specified by KTM for this model

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  6. Add New Oil
    Insert a funnel into the fill port. Pour in exactly 0.8 liters of KTM-approved gear oil. (Consult the manual or bottle for the correct type; Motorex 10W-40 is a common recommendation).
    • Be careful not to overfill. On the KTM 125SX, add oil until it just starts to weep out the oil level bolt (some owners use this method for precision)

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    • If you notice oil overfilling or spilling, pause and give it time to settle.
  7. Check the Oil Level
    With the bike upright and level, check for leaks. If your 125SX has an oil level check bolt, remove it temporarily to ensure oil “seeps” out gently—this confirms proper filling

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  8. Reinstall the Oil Fill Cap
    With oil added and the level confirmed, reinstall the cap. Use pliers to gently snug it down—KTM recommends making it tight enough to avoid loosening during rides, but be careful not to overtighten

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  9. Clean Up
    Dispose of old oil responsibly—most auto parts stores offer recycling. Wipe away any spillage around the engine.
  10. Start & Inspect
    Run the engine for a minute and inspect for leaks under the drain plug and around the fill cap. If you see drips, stop and retighten the corresponding plug.

2020 KTM 125SX Special Call-Outs

  • Crush washer replacement is critical for avoiding leaks in KTM engines
  • 0.8 liters is the target capacity–using the “weep” method at the level bolt ensures you’re on target and not overfilling

  • Torque specs matter–KTM's 20Nm/14.8ft-lb should always be used to avoid stripping or under-tightening
  • If unsure about oil type or specs, consult your KTM owner’s manual or the official MotoSport.com KTM parts fiche

Conclusion

Changing the oil on your 2020 KTM 125SX is a straightforward job with the right tools. By following KTM’s recommended procedures and specs, you’ll keep your bike running strong and protect your investment for every ride. For genuine parts, filters, and recommended fluids, trust MotoSport.com—built for riders, by riders.

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Shop Oil Fillers and Drain Plugs for a 2020 KTM 125SX 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.