How to Change the Oil in a 2012 GAS GAS TXT PRO 125

Shop parts for a 2012 GAS GAS TXT PRO 125 Dirt Bike.

Keeping your 2012 GAS GAS TXT PRO 125 running in peak condition means regular maintenance, and one of the most critical tasks is changing the gear oil. This guide—exclusive to MotoSport.com—covers every step, highlighting GAS GAS-specific details and owner tips for a robust, safe oil change.

Tools and Supplies Needed

  • Socket set or spanners (wrenches)–Metric, correct size for the drain bolt, usually 6–8mm (double-check to prevent stripping)
  • Oil catch pan
  • Clean rags
  • Funnel
  • Measuring cup or jug (marked in quarts/cc)
  • Replacement gear oil–Specialist gear oil like Gro or Motul Transoil; GAS GAS recommends high-quality 75W-80 or 75W-90 gear oil
  • Torque wrench (recommended)
  • Gloves (optional, but keeps hands clean)
  • New drain plug washer (recommended, optional)

Oil Capacity and Type for 2012 GAS GAS TXT PRO 125

  • Gear oil capacity: 0.42 quarts (approx. 0.4 liters or 420 ml) (capacity per manufacturer for similar model years)
  • Recommended oil type: Specialist gear oil, such as 75W-80 or 75W-90 (avoid regular engine oil–use for wet clutch systems)

Model-Specific Notes

  • The 2012 TXT PRO 125 uses a wet clutch–always use gear oil designed for this system, not motor oil.
  • The drain plug is easily stripped if overtightened; snug and not overtight–never force it, always use a fresh washer when possible.
  • The fill plug is accessed on the top of the right-side case.
  • Check the air filter after every oil change while your panels are off.

Steps to Change the Oil

  1. Warm up the motorcycle
    Start the engine and let it idle for a few minutes so the gear oil heats up; this helps the oil flow out more completely and suspends debris in the oil.
  2. Stabilize the bike
    Place the bike upright on a level surface using a bike stand to prevent accidental spills.
  3. Remove skid plate (if equipped)
    Use a socket to remove the bolts and set the skid plate aside for easier access.
  4. Prepare to drain
    Position your oil catch pan directly under the drain plug. Make sure the plug and surrounding engine area are clean to prevent debris from falling into the gearbox.
  5. Remove the drain plug
    Use the correct spanner/socket (typically 8mm, but confirm). Turn counterclockwise and carefully remove. Let the oil drain out completely. Inspect the drained oil for metal shards or contamination.
  6. Replace washer and reinstall drain plug
    Inspect or replace the washer/gasket. Lightly clean the bolt threads. Reinstall the drain plug by hand and finish with a wrench, tightening only snug. Do not overtighten. (Recommended: 6–8 Nm, consult your owner's manual for exact spec.)
  7. Remove the fill plug
    Located on the top/right case (often marked or with a slot head). Remove it and set aside.
  8. Pour in new oil
    Using a funnel and measuring jug, add exactly 0.42 quarts (420 ml) of approved gear oil. Overfilling may lead to clutch issues; under-filling causes severe wear.
  9. Wait and check for leaks
    Allow the oil to settle for a minute. Check around the drain plug for leaks. Wipe up any drips.
  10. Reinstall fill plug
    Wipe it clean, thread in by hand, and snug gently with a wrench.
  11. Restart the engine and inspect
    Start the engine and let it idle for a minute. While running, check for leaks at the drain plug and case. Shut off and re-check oil level (if there's a check plug or sight glass).
  12. Dispose of old oil responsibly
    Take used gear oil to a recycling facility–do not dump it.
  13. Reinstall skid plate and clean up

Tips and Owner Call-Outs Specific to the 2012 GAS GAS TXT PRO 125

  • Don't Over-tighten. The alloy casing on GAS GAS gearboxes is soft. Over-tightening will strip the threads. Always use a torque wrench when possible and “snug” the plug, not tight.
  • Oil Selection: Clutch feel and performance can shift noticeably between oil types; many TXT owners swear by Gro or Motul Transoil gear oils. Avoid ATF (automatic transmission fluid) unless you have specific clutch issues and know what you're doing.
  • Check for debris: If you see excess metal flakes in the old oil, inspect the clutch and gearbox before further riding.
  • Regular schedule: For trials riding, change oil every 20–30 hours of use or sooner if you ride in muddy or wet conditions.
  • Air filter tip: After an oil change is a great time to clean and re-oil your air filter.

Conclusion

With basic hand tools and attention to detail, you can safely and quickly change the gear oil in your 2012 GAS GAS TXT PRO 125, maintaining performance and reliability ride after ride. Always refer to your specific owner's manual for torque specs and oil recommendations, and trust MotoSport.com for all your OEM and aftermarket maintenance needs.

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Shop Tools for a 2012 GAS GAS TXT PRO 125 Dirt Bike.

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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.