How to Change the Oil in a 2021 KTM 150SX: The MotoSport.com Guide

Shop parts for a 2021 KTM 150SX Dirt Bike.

Changing the oil in your 2021 KTM 150SX is essential for optimal performance and engine longevity. This two-stroke model does not require regular motor oil changes like a four-stroke, but you do need to change the transmission (gear) oil at routine intervals. Here's a proprietary, professional MotoSport.com guide tailored for your bike, including all the tools needed, step-by-step instructions, and specific model call-outs you need to know.

Tools and Supplies Needed

  • 8mm T-Handle or socket wrench (for drain plug)
  • Torque wrench (for tightening drain plug)
  • Drain pan/catch can
  • Funnel
  • Replacement gear oil (SAE 10W-40 or as specified by KTM)
  • New crush washer (recommended to prevent leaks)
  • Clean rags
  • Latex or nitrile gloves (optional but recommended)
  • Pliers (for snugging fill cap as per KTM guidance)

Special Note for the 2021 KTM 150SX

  • This is a two-stroke motorcycle. You're changing the transmission or gear oil, not engine oil as you would on a four-stroke.
  • The oil capacity is approximately 0.8 liters for the 150SX.
  • Always use the recommended type and volume of oil indicated in your KTM owner's manual.
  • Always replace the crush washer on the drain bolt to prevent leaks.
  • Tighten the drain plug to 20 Nm (14.8 ft-lbs) with a torque wrench for best sealing.
  • KTM recommends you snug the oil fill cap slightly with pliers to prevent it from loosening during rides.

Step-by-Step Oil Change Instructions

  • Warm Up the Bike
    Start your KTM 150SX and let it idle for a few minutes. This warms the transmission oil so it flows out easier and carries away more contaminants. Caution: The oil and engine cases may become hot.
  • Prepare the Work Area
    Place your bike on a level stand.
    Position your drain pan directly under the transmission drain plug.
  • Remove the Oil Fill Cap
    Remove the fill cap on the right side of the engine. This allows the old oil to drain more freely.
    If you have a skid plate and it blocks the drain bolt, you may need to remove it for better access. There are also aftermarket drain aids like oil change funnels that can reduce mess if you commonly work around the skid plate .
  • Loosen and Remove the Drain Bolt
    Use an 8mm T-handle or socket to carefully loosen and remove the transmission drain bolt (located on the underside of the engine case).
    Allow the oil to fully drain into the pan. Tip: Avoid dropping the bolt into your oil pan.
  • Inspect and Clean the Drain Bolt
    Most KTM models have a magnetic drain bolt to collect metallic debris. Wipe off any debris. A small amount is normal; larger chunks could indicate wear or damage .
    Replace the crush washer on the bolt.
  • Reinstall the Drain Bolt
    Screw in the drain bolt finger-tight, then use a torque wrench to tighten to 20 Nm (14.8 ft-lbs) . Overtightening can strip the threads or crush the washer excessively.
  • Add New Gear Oil
    Place a funnel in the fill port and pour in 0.8 liters of the recommended oil .
    If unsure, pour gradually and check the sight glass (if equipped) or add oil until it reaches the bottom of the fill threads or weep hole as specified for your KTM.
  • Install the Oil Fill Cap
    Reinstall the fill cap and use pliers to gently snug it, as KTM recommends, so it remains secure during riding .
  • Check for Leaks and Wipe Down
    Clean off all excess oil around the fill and drain areas. Start the bike, let it idle briefly, and check for leaks around the drain bolt and fill cap. Tighten slightly more if necessary, but do not overtighten.
  • Proper Disposal
    Dispose of your used oil at an approved recycling center or auto parts store.

Model-Specific Tips and Reminders for the 2021 KTM 150SX

  • Always use the oil type and capacity listed in your owner's manual. For the 2021 150SX, KTM generally recommends SAE 10W-40 transmission oil, but always verify your specific manual.
  • The magnetic drain plug is designed to help you catch early signs of engine wear. A little debris is normal, but large chips or excessive metallic particles may require further inspection.
  • If you ride in muddy or wet conditions, consider changing your gear oil more frequently to ensure internal parts stay properly lubricated.
  • Ensure you do not overfill—excess oil can cause excess crankcase pressure or leaks.

Pro Tip from MotoSport.com

A spill-free oil change is easier if you tip the bike slightly away from the drain plug side after most of the oil has drained out, ensuring you remove as much used oil as possible. Always have extra rags on hand for drips and splashes.

Changing your KTM 150SX's transmission oil is straightforward, but following these steps carefully will help you avoid mess, leaks, or costly mistakes—and keep your two-stroke ripping at its best for every ride.

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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.