How to Change the Oil in a 2009 KTM 105SX

Shop parts for a 2009 KTM 105SX Dirt Bike.

The 2009 KTM 105SX is a motocross two-stroke dirt bike that requires regular oil changes to ensure maximum performance and durability. Proper maintenance keeps your engine running smoothly during those demanding MotoSport.com rides. This step-by-step guide covers the entire oil change process, lists all the tools and supplies you need, and highlights essential call-outs unique to this model.

Tools and Supplies Needed

  • 10mm or 13mm socket or wrench (check your drain plug size; most will be 13mm)
  • Drain pan
  • Clean funnel
  • New gearbox oil (KTM recommends 10W-40 or 10W-50 for two-stroke gearbox; 0.3 L to 0.4 L depending on use–refer to your owner's manual or markings on your case)
  • Replacement crush washer
  • Shop towels or paper towels
  • Torque wrench
  • Contact cleaner (optional, for cleaning drainage area)
  • Gloves

Preparation

  • Make sure the bike is on a level surface. It's best to warm up the engine for a few minutes before an oil change; this helps the oil flow out more thoroughly.
  • Put on gloves to protect your hands from hot oil and chemicals.
  • Gather all tools and place a drain pan underneath the drain plug area to avoid spills.

Step-by-Step Guide

  • Remove the gear oil fill cap:
    • On the KTM 105SX, this is typically located on the right side of the engine case, just above the kickstarter.
    • Removing this cap helps the oil drain more completely by preventing vacuum lock.
  • Remove the oil drain plug:
    • Locate the gear oil drain bolt under the engine, usually around the right side near the bottom front part of the case.
    • Use a 13mm wrench or socket to carefully loosen and remove the plug. Watch out for hot oil.
    • Let the oil drain fully into the pan. Tilt the bike gently side to side to remove as much old oil as possible. Some recommend leaving the bike upright for several minutes.
    • Inspect the drain plug for metal shavings. A moderate amount is normal. Clean the drain plug and the area around the drain hole.
  • Check and replace the crush washer:
    • Always inspect the crush washer on the drain plug. Replace it to prevent leaks, as used washers can become misshapen and fail to seal properly.
  • Reinstall the oil drain plug:
    • Thread the clean plug (with new washer) back into the engine by hand to avoid cross-threading.
    • Use a torque wrench to tighten the drain plug to KTM's recommended torque specification (typically 10-15 Nm for smaller two-stroke models, but always check your manual). Over-tightening can strip the threads or crack the case.
  • Fill with new gear oil:
    • Insert a clean funnel into the oil fill port.
    • Slowly pour in the recommended amount (0.33 to 0.4 liters for this model). Overfilling can cause leaks and excessive crankcase pressure, while under-filling risks harming the transmission.
    • Wait a moment, then check the oil level. On the 105SX, there is often a sight glass or check bolt. Add oil until the correct level is visible or oil begins to seep out of the check hole (with the bike level).
  • Reinstall the fill cap:
    • Screw the fill cap back on securely by hand.
    • Use pliers to snug it (recommended by KTM) but do not over-tighten. This ensures the cap doesn't loosen during your next ride.
  • Start and inspect:
    • Wipe down any oil spills and start the engine. Let it idle briefly, then shut it off and check for leaks at the drain plug and fill cap.
    • Recheck the oil level and top off if needed.

Model-Specific Call-outs for 2009 KTM 105SX

  • Use a high-quality 10W-40 or 10W-50 motorcycle-specific gear oil. Do not use standard automotive oils as they do not have the correct properties for two-stroke transmissions and clutches.
  • The recommended oil volume is approximately 0.33-0.4 liters (see your owner's manual for exact figure). Overfilling may cause leaks from pressure relief vents.
  • This model does not have an oil filter—only a drain plug, so maintenance is simpler.
  • When cleaning the drain plug, you may notice a small amount of metallic debris; this is normal—excessive amounts may indicate internal wear and should be inspected by a mechanic.
  • If you race or ride hard, consider changing the oil more frequently—every 2-4 hours of ride time under MotoSport race conditions.

Helpful Tips from MotoSport.com

  • Dispose of your used oil responsibly at a recycling center or auto parts store.
  • For frequent racers, mark your oil change intervals on a log or with a piece of tape somewhere hidden on the frame.
  • If you ever notice milky or discolored oil, check for signs of water intrusion, which could indicate a failing seal or gasket.

Conclusion

Changing the oil regularly on your 2009 KTM 105SX protects your bike from costly damage and keeps you competitive on the track. By following this MotoSport.com guide, you can keep your bike running at its peak—and extend the life of every component. Happy riding.

Related Shopping Categories

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Shop Oil Fillers and Drain Plugs for a 2009 KTM 105SX 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.