How to Change the Oil in a 2011 KTM 105SX

Shop parts for a 2011 KTM 105SX Dirt Bike.

Keeping the transmission and clutch of your 2011 KTM 105SX in top shape is critical for performance and longevity. Following the correct oil change procedure will help you get the most out of your bike. Below is your complete, proprietary step-by-step MotoSport.com guide for changing the oil on this specific KTM dirt bike model, with important call-outs unique to the 105SX.

Tools and Supplies Needed

  • 8mm or 13mm socket (verify based on aftermarket parts, but KTM OEM is usually 13mm for the drain bolt)
  • Socket wrench and extension bar
  • Torque wrench
  • Drain pan
  • Funnel
  • Clean rags
  • Fresh gear oil (KTM recommends Motorex Topspeed 4T 15W50 for the 2011 105SX or an equivalent 10W-40/15W-50 transmission oil)
  • New drain bolt washer/gasket (recommended but reuseable if in good shape)
  • Contact cleaner or brake cleaner (optional, for cleaning drain bolt threads)
  • Shop stand or triangle side stand to keep the bike upright
  • Gloves (optional but highly recommended to protect hands)

Important Notes for the 2011 KTM 105SX

  • This model is a two-stroke with a separate transmission oil reservoir–the oil you are changing is transmission/gear oil, not premix oil for the engine.
  • Recommended oil volume is 0.5 liters (500 ml).
  • Tighten the oil drain plug to 15 Nm (Newton meters) for proper sealing and to avoid stripping the threads.
  • Check for any leaks after refilling, as the gasket under the drain plug is a common point of seepage if not replaced or properly seated.
  • Run the engine briefly after oil change and recheck oil level and for leaks.

Step-by-Step Oil Change Process

  • Warm Up the Engine
    Start your engine and let it idle for 2–3 minutes. This warms the oil, making it flow more easily and ensuring it carries away contaminants and old debris when draining. Be careful—oil and engine cases will be hot.
  • Position the Bike
    Place your 2011 KTM 105SX on a level surface using a shop or triangle side stand. The bike should be as upright as possible to ensure full drainage.
  • Remove the Oil Filler Cap
    Loosen and remove the oil filler plug (located on the right side of the engine case). This allows air to enter and the transmission oil to drain more quickly and completely.
  • Locate and Remove the Drain Plug
    Find the oil drain bolt underneath the transmission case. Position your drain pan under the bolt, then use the socket wrench to slowly loosen and remove the drain plug (be careful not to drop it into the pan). Let the oil drain completely; tilting the bike slightly can help evacuate the last bit of old oil.
    Inspect the old oil for metal particles or discoloration. Some fine particles are normal, but excess debris could indicate a problem.
  • Clean and Inspect the Drain Plug
    If your drain plug uses a magnetic tip, wipe it clean of any metal shavings. Inspect the gasket/washer: if it's damaged or compressed, replace it to ensure a proper seal on reinstallation.
  • Reinstall the Drain Plug
    Refit the plug with its washer and tighten to 15 Nm using a torque wrench. Do not overtighten—it is easy to strip the small aluminum threads.
    Wipe off any excess oil from the case before proceeding.
  • Refill with Fresh Gear Oil
    Place your funnel in the fill port and carefully pour in 0.5 liters (500 ml) of recommended gear oil (Motorex Topspeed 4T 15W50 or suitable alternative). Allow time for the oil to settle, avoiding overfill.
  • Check Oil Level and Reinstall Filler Cap
    With the bike level, verify the oil is at the correct level by checking sight window or dipstick (if equipped, but many KTM two-strokes do not have one). Reinstall the oil filler cap and tighten it securely.
  • Final Inspection
    Wipe away any spilled oil, start the engine, and let it idle for a minute. Shut down and check for any leaks around the drain plug or filler cap. Adjust oil level if needed.

Quick Tips Specific to the 2011 KTM 105SX

  • Change gear oil every 5–10 hours of riding or after every couple of races, as the small capacity means the oil degrades rapidly under harsh use.
  • Do not confuse transmission/gear oil changes with premix—this model requires both correct premix for the fuel and regular gear oil changes for the transmission.
  • If you notice excessive clutch slippage or shifting issues, inspect the old oil for contaminants and consult your manual.
  • Always dispose of used oil properly at a recycling center or approved collection site.

By following these steps and calling out the specifications for your 2011 KTM 105SX, you'll ensure your bike stays ready for every ride, every time. For more KTM parts, oils, tools, and gear, MotoSport.com is your trusted source for everything you need.

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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.