How to Change the Oil in a 2021 GAS GAS TXT GP 250

Shop parts for a 2021 GAS GAS TXT GP 250 Dirt Bike.

This proprietary guide from MotoSport.com walks you step-by-step through changing the gear oil on a 2021 GAS GAS TXT GP 250, ensuring optimal clutch and transmission performance while extending the life of your trials bike.

Tools & Materials Needed

  • 8mm or 10mm socket/wrench (check your drain and fill plug size before starting)
  • Allen key set (usually 5mm or 6mm for the fill bolt)
  • Drain pan
  • Funnel
  • Clean rags
  • Measuring cup (to ensure precise oil volume)
  • Fresh gear oil (Quality 75W transmission oil or the manufacturer’s recommended gear oil. GRO, Putoline, or Motul are commonly preferred.)

Preparation Before You Start

  • Warm up the engine for 3–5 minutes to let the oil become less viscous. This ensures a more complete drain.
  • Ensure your work area is well ventilated and the bike is on a stable, flat stand, ideally with the skid plate removing access to the drain bolt if necessary.
  • Have a new sealing washer/crush washer handy for the drain bolt (recommended, but not required every time).

Steps to Change the Oil

  1. Locate the Drain Bolt:
    • The oil drain bolt is found on the underside of the engine, centered under the crankcase. There is a dedicated hole in the bash plate for access.
  2. Remove the Drain Bolt:
    • Position your drain pan under the hole, then remove the drain bolt with the socket or wrench.
    • Let the used oil fully drain into the pan. This can take several minutes. Always inspect the oil for metallic particles, which could indicate internal wear.
  3. Replace the Crush Washer:
    • For a reliable seal, replace the old crush washer with a new one before reinstalling the drain bolt.
  4. Reinstall the Drain Bolt:
    • Wipe the bolt and drain area clean with a rag and refit the bolt. Do not overtighten to avoid stripping the threads or cracking the case. Hand-tighten, then give it a gentle half turn with your wrench.
  5. Access the Fill Plug:
    • On the 2021 GAS GAS TXT GP 250, the oil fill plug is just above the gear lever on the right side of the engine, typically a bolt with an Allen head.
    • Remove the fill bolt.
  6. Refill with Fresh Oil:
    • Insert a funnel into the fill hole and pour in the manufacturer’s recommended oil quantity for the TXT GP 250. This is generally ~380ml–400ml of quality transmission oil.
    • Take care not to overfill; adding too much oil can cause clutch drag or leaks. Use your measuring cup for accuracy.
    • Allow a few minutes for the oil to settle and double-check the oil level if your model has an inspection window or dipstick (most trials bikes rely solely on measured fill quantity).
  7. Reinstall the Fill Plug:
    • Wipe the area and install the fill plug. Again, snug but not overtightened.
  8. Final Checks:
    • Start the bike and let it idle for a couple of minutes. Inspect for leaks around the drain and fill plugs.
    • Dispose of the old oil according to local environmental guidelines.

2021 GAS GAS TXT GP 250 Callouts & Specific Advice

  • The TXT GP 250 uses a premix lubrication system for the engine (2-stroke oil mixed with gas), but the gearbox requires routine oil changes as described above.
  • Use a high-quality synthetic or semi-synthetic transmission oil for optimal shifting and clutch life. GRO Transmission Oil is commonly recommended among riders.
  • The oil volume is small (about 400ml), so precise measurement is important. Overfilling can hurt clutch performance.
  • Do not overtighten drain and fill bolts—the threads in these cases are easily damaged. If using a torque wrench, check your manual’s specified torque settings.
  • Always run the engine briefly and check for leaks after your oil change.
  • Trials bikes like the TXT GP 250 are designed for low-output, high-finesse riding, so clean oil is critical for the delicate clutch and transmission function.

Common Questions and Additional Tips

  • How often should I change the oil?
    It’s best to change the gear oil every 20–30 hours of riding, or sooner in wet or exceptionally muddy conditions.
  • What if the oil looks gray or contains metallic particles?
    If your drained oil is silvery or metallic, contact a GAS GAS dealer for a professional inspection—this may indicate internal wear.
  • Do I need to use GAS GAS-branded oil?
    While it’s not required, using the manufacturer’s recommended oil ensures compliance with warranty recommendations and optimal component life.

By following these precise steps, your 2021 GAS GAS TXT GP 250 will be ready for more hours of reliable, high-performance trials riding. For more GAS GAS how-tos and OEM-quality parts, visit MotoSport.com.

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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.