How to change the oil in a 2009 GAS GAS TXT PRO 125 Dirt Bike

How to Change the Oil in a 2009 GAS GAS TXT PRO 125

Shop parts for a 2009 GAS GAS TXT PRO 125 Dirt Bike.

Maintaining the transmission oil in your 2009 GAS GAS TXT PRO 125 is key to ensuring longevity and peak performance, especially under the stress of trials riding. Below you'll find a step-by-step guide, tailored for this specific model year, curated exclusively for MotoSport.com readers.

Tools & Supplies Needed

• Metric socket set (especially 8mm, 10mm, and 13mm)
• Metric wrenches (spanner, commonly 13mm for drain bolt)
• Torque wrench (for proper drain bolt installation)
• Rubber or latex gloves
• Drain pan
• Clean rags
• Parts cleaning brush (for cleaning around the oil area)
• New gear/transmission oil (see capacity and spec below)
• Oil funnel (narrow tip for small filler area)

Oil Type – Capacity:

• Recommended oil: High-quality synthetic gear oil, 75W–80 (brands like AMSOIL, Motul, or official GAS GAS gear oil)
• Capacity: Approximately 0.58 quarts (550ml) for this engine and model year

Step-By-Step Oil Change Procedure

• Warm Up the Engine:
  Run your TXT PRO 125 for 3-5 minutes. This helps the old oil flow out more completely and stirs up debris for removal.
• Stabilize the Motorcycle:
  Use a lift stand to keep your bike upright and level. This is especially important for trials bikes like the TXT PRO 125 to ensure all old oil drains out properly .
• Locate the Drain Plug:
  On the right-hand side underneath the engine, you'll find the oil drain bolt. It's usually a 13mm bolt. Clean the area with a rag to prevent debris from falling in.
• Position the Drain Pan:
  Place your drain pan directly below the drain bolt to capture the used oil.
• Remove the Drain Bolt:
  Using your wrench, carefully loosen and remove the bolt. Oil will flow quickly. Let it drain until the flow stops completely. Use a clean rag to wipe drips and debris from the opening.
• Inspect and Clean the Bolt:
  Some bolts have a magnetic tip to capture metal filings; clean this thoroughly. Check the condition of the drain bolt washer or seal—replace if damaged or overly compressed.
• Reinstall the Drain Plug:
  Hand-thread the plug first to avoid cross-threading, then tighten snug, but do not over-torque. The threads in GAS GAS cases are soft aluminum and over-tightening can strip them .
  • Recommended torque: 10-12 Nm (lightly snug)
• Remove the Oil Filler Cap:
  On top of the right engine case, locate and unscrew the oil fill cap. Some models may have a breather hose attached—move it aside.
• Add New Oil:
  Using a funnel, add 550ml of 75W–80 synthetic gear oil . Pour slowly to prevent spillage.
• Check Level & Secure Filler Cap:
  Some models have a sight glass or level bolt; ensure oil is at the proper level per your manual. Reinstall the filler cap securely.
• Run & Re-Check for Leaks:
  Start the bike and let it idle for a couple of minutes. Shut it off and check the drain/bottom area for leaks.
• Dispose of Used Oil Properly:
  Place old oil in an approved container and bring it to a local recycling center.

Model-Specific Considerations for GAS GAS TXT PRO 125 (2009)

• The drain and filler bolts are soft aluminum; always use the exact size spanner for loosening/tightening to prevent stripping .
• Only use the specified oil type and volume: Overfilling can cause clutch drag; underfilling risks transmission damage .
• These models do not have replaceable oil filters; dirt and metal fragments are caught on the magnetic plug, so keep it clean.
• Changing oil more frequently (every 10–20 hours of use) is highly recommended for trials bikes, due to clutch abuse and high internal temperatures.
• If you notice milky oil, water may be leaking into the transmission (bad seals/gasket)—address this immediately to avoid bearing failure.
• On the TXT PRO 125, draining and refilling oil is a straightforward process, but always double-check the torque on all bolts as mentioned; overtightening is a recurring issue .

Final Tips

• Keep the bike clean around the oil change area to avoid introducing dirt.
• Record the date and hours of operation after each oil change for maintenance tracking.
• Inspect clutch function after the change; fresh oil may slightly alter feel or engagement point.

Changing the oil in your 2009 GAS GAS TXT PRO 125 is a straightforward, crucial maintenance item that ensures your trials machine continues to perform at its best. For all parts, tools, and premium lubricants, trust MotoSport.com to keep you riding.

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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.