How to Change the Oil in a 2021 GAS GAS MC 85 Dirt Bike

Shop parts for a 2021 GAS GAS MC 85 Dirt Bike.

Changing the oil in your 2021 GAS GAS MC 85 is essential maintenance that keeps your bike running smoothly and ensures longevity and performance. This guide, proprietary to MotoSport.com, outlines all the tools you'll need, step-by-step instructions, and essential, model-specific insights for a clean and successful oil change.

Tools & Materials Needed

  • 8mm T-handle or socket wrench (for drain plug)
  • Oil drain pan
  • 500cc of quality gear oil (such as Motul Trans Oil or Maxima MTL)
  • Funnel (ideally a 3D printed, threaded type for spill-free filling)
  • Shop rags or paper towels
  • Contact cleaner (e.g., Maxima Contact Cleaner)
  • New crush washer (recommended during reassembly)
  • Torque wrench (to torque plug to 15 Nm)
  • Screwdriver (for brake pedal adjustment hack)

Step-By-Step Oil Change Instructions

  1. Warm Up the Bike
    • Start your MC 85 and let it idle for a few minutes to warm up the oil. Warm oil drains more thoroughly.
  2. Prepare the Work Area
    • Place the bike on a stand so it is upright and stable.
    • Position the oil drain pan beneath the drain plug.
  3. Access the Drain Plug
    • Model-Specific Call-Out: On the 2021 GAS GAS MC 85, the rear brake pedal can block access to the drain plug. Use this hack:
      • Separate the brake pads to push the piston in fully.
      • Push the brake pedal down and temporarily wedge a screwdriver between the pedal and the frame to hold it down and clear the drain plug area for access.
  4. Remove the Drain Plug
    • Use your 8mm wrench or T-handle to loosen and remove the oil drain plug.
    • Let the old oil drain completely into your pan. Tilt the bike slightly side to side to ensure full drainage.
    • Inspect the oil for debris. Small metallic flecks are normal, but large chunks or excessive shavings can indicate gearbox issues.
  5. Clean Up
    • Wipe the drain plug and the area around the sump clean with contact cleaner and a rag for a proper seal.
    • Replace the crush washer on the drain plug to prevent leaks.
  6. Reinstall the Drain Plug
    • Thread the drain plug in by hand, then tighten with your wrench.
    • Torque the drain plug to 15 Nm as specified. Over-tightening can strip the threads or crack the case.
  7. Refill with Oil
    • Use a funnel–preferably a spill-proof, threaded type–to slowly pour in 500cc of gear box oil (such as Motul Trans Oil or Maxima MTL).
    • Ensure the funnel or fill port is clean before pouring in the oil.
    • Double-check you are using the correct type and amount—this engine does not have an oil filter; it uses gear box oil only.
  8. Check the Oil Level
    • Some MC 85s have a level window or bolt to verify proper fill. Confirm according to your manual, or measure precisely before pouring.
  9. Final Checks
    • Start the bike and let it idle for a minute, then shut it off and check for leaks around the drain plug.
    • Reinspect your oil level and top off if necessary.
  10. Clean Up & Dispose of Oil
    • Dispose of used oil properly at a local waste oil recycling center.
    • Clean your tools, replace any covers, and remove the screwdriver from your brake lever.

Key Call-Outs for the 2021 GAS GAS MC 85

  • The oil volume is precisely 500cc. Over or underfilling can harm clutch and gearbox performance.
  • Recommended gear oil types include Motul Trans Oil and Maxima MTL, both trusted by shops and riders for this model.
  • Torque spec for the drain plug is 15 Nm. Never overtighten to avoid thread damage.
  • There is no replaceable oil filter; this is a two-stroke transmission oil service.
  • Watch for the brake pedal obstructing the drain plug. Use the piston and screwdriver hack if needed for easier access.
  • Always inspect drained oil for metallic debris as an early indicator of potential issues.

Final Tips

  • Change the oil at intervals recommended in your owner's manual or after every few rides for best gearbox life.
  • Wipe up any spills to avoid attracting dirt and ensure you re-torque bolts after your first ride if you notice seepage.

With the right tools, careful attention to detail, and a little time, your 2021 GAS GAS MC 85 will be ready for more rides with fresh, clean gear oil. For any parts or gear oil needs, trust MotoSport.com to keep your bike running its best.

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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.