How to Change the Oil in a 2025 GAS GAS MC 85

Shop parts for a 2025 GAS GAS MC 85 Dirt Bike.

Keeping your 2025 GAS GAS MC 85 running at its best means regular maintenance—including changing the gear oil. This step-by-step MotoSport.com guide details the tools you’ll need, model-specific tips, and every key step to get your mini motocrosser’s transmission oil changed the right way.

Tools & Supplies Needed

  • 8mm T-handle or socket wrench
  • Torx or Allen wrench (if required for skid plate removal)
  • Drain pan
  • Clean funnel (3D printed or rubber-tipped preferred)
  • Crush washer (new, recommended)
  • Torque wrench (capable of measuring 15 Nm)
  • Brake cleaner or contact cleaner
  • Shop towels
  • 500cc (0.5L) quality transmission oil (such as Motul Trans Oil or Maxima MTL)
  • Flathead screwdriver (for brake pedal adjustment, see below)

Special Call-Outs for the 2025 GAS GAS MC 85

  • Gear oil capacity is 500cc (0.53 US quarts). Overfilling or underfilling can affect clutch performance and shifting. Double-check your fill.
  • The drain bolt is partially obstructed by the rear brake pedal. You may need to move the pedal out of the way—see model-specific instructions below.
  • Use a new crush washer on the drain plug each oil change to prevent leaks.
  • Tighten the drain plug to 15 Nm (Newton-meters). Over-tightening can strip threads; under-tightening can lead to leaks.

Step-by-Step Oil Change Instructions

  1. Warm Up the Engine Briefly
    Start the bike and let it idle for 2–3 minutes. Warming the oil helps it drain more completely along with any contaminants.
  2. Prepare the Bike and Tools
    Shut the bike off. Place the MC 85 on a stable stand. Gather all your tools and supplies. Ensure your drain pan is ready and positioned under the drain bolt.
  3. Access the Drain Bolt
    The drain bolt sits behind the rear brake pedal. For easier access:
    • Use a flathead screwdriver to pry the brake lever slightly downward (do not damage the master cylinder.)
    • Alternatively, compress the rear brake caliper piston to allow the pedal to drop farther. (Push the caliper toward the disc to gain space.)
    This hack clears the brake pedal from blocking your hex socket or 8mm T-handle wrench from the drain bolt.
    (If your MC 85 has a skid plate covering the drain area, remove it with a Torx/Allen wrench as needed.)
  4. Remove the Drain Plug and Drain the Oil
    Loosen the drain plug with an 8mm wrench. Allow oil to fully drain into your pan.
    • Tip: Lean the bike gently side-to-side while draining to help evacuate all old oil.
    While draining, inspect the magnetic drain plug for metallic debris—tiny flecks are normal, but large pieces indicate transmission wear.
  5. Clean and Inspect Components
    Clean the drain plug using brake cleaner/contact cleaner. Also wipe down the bolt threads and crush washer seat.
    If the crush washer is damaged or flattened, replace it. Using a new washer helps maintain a tight, leak-free seal.
  6. Reinstall the Drain Plug
    Refit the cleaned drain plug (with new crush washer) and hand-tighten. Using your torque wrench, finish by tightening to 15 Nm. Do not over-tighten.
  7. Add New Gear Oil
    Insert a clean funnel into the oil fill port (on the right engine cover), and carefully pour in 500cc of quality transmission oil (Motul Trans Oil, Maxima MTL, or OEM equivalent recommended).
    Slow, steady pouring helps prevent air pockets or messy spills—some MC 85 owners favor a funnel that screws directly into the case threads.
  8. Check Oil Level
    The MC 85 features a check bolt or sight glass to verify correct oil level. Remove the check bolt with your wrench—oil should just begin to seep from the hole. If no oil escapes, add a tiny amount more; if too much pours out, let it finish draining to the correct level.
  9. Reinstall All Parts and Clean Up
    Refit and snug any check/fill bolts. Wipe away any oil residue. Reinstall the skid plate (if equipped). Reposition the rear brake pedal to its correct place and ensure smooth operation.
  10. Start and Inspect
    Run the engine for 2–3 minutes, then shut down. Inspect the drain bolt and case for leaks. Make final adjustments as needed.

Additional Tips for Your 2025 GAS GAS MC 85

  • Follow service intervals from your owner’s manual; change oil every 5–10 hours of riding or after racing.
  • Inspect your drain plug every oil change for excessive debris.
  • Always use high-quality, recommended transmission oil for clutch and gearbox longevity.
  • Keep your work space clean—debris in your oil or transmission can lead to costly repairs.

Regular maintenance builds confidence—as does knowing MotoSport.com supplies all OEM-quality oils, crush washers, and tools you need for the job. Check your chain tension and air filter while you’re at it and get back on the track.

Related Shopping Categories

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Shop Tools for a 2025 GAS GAS MC 85 Dirt Bike.

Shop Oil Fillers and Drain Plugs for a 2025 GAS GAS MC 85 Dirt Bike.

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.