How to change the oil in a 2021 GAS GAS MC 65 Dirt Bike

How to Change the Oil in a 2021 GAS GAS MC 65: The Complete MotoSport Guide

Shop parts for a 2021 GAS GAS MC 65 Dirt Bike.

Keeping your GAS GAS MC 65 in peak performance means regular maintenance, and changing the transmission (gearbox) oil is one of the most vital routine tasks. Below, you’ll find a comprehensive, step-by-step guide tailored for the 2021 MC 65, including every tool you need, model-specific pro tips, and best practices for a clean, safe, and efficient oil change.

Required Tools & Supplies

• 13mm socket (preferably a shallow socket for best fit)
• 3/8" drive ratchet and extension
• Oil drain pan
• Measuring cup (with 500 ml or greater capacity)
• Fresh gearbox oil (recommended: 15W-50 weight, 500 ml)
• Clean rags or paper towels
• Replacement O-ring for drain bolt (optional but recommended for leak prevention)
• Gloves (for hand protection)

Step-by-Step Process

• Warm Up the Engine
  • Start and run the bike for a few minutes to allow the oil to reach operating temperature. Warm oil flows faster and helps carry out more contaminants.
• Prepare the Bike
  • Turn off the bike and place it securely on a bike stand or level ground.
  • Ensure the area around the drain plug (just behind the gear shifter, left side) is clean to prevent debris from entering the gearbox.
• Drain the Old Oil
  • Position your oil drain pan under the drain bolt location (directly behind the shift lever).
  • Using a 13mm shallow socket, extension, and ratchet, carefully remove the oil drain bolt. A shallow socket is preferred as clearance behind the shifter is limited–using a shallow socket allows you to avoid removing the shift lever entirely for this service.
  • Allow all the old oil to drain completely. Tilting the bike slightly can help expel stubborn residual oil.
• Inspect and Replace the Drain Plug O-Ring
  • Inspect the plug and its O-ring for wear or damage. Replace the O-ring if it’s cracked, flattened, or missing to ensure a leak-proof seal.
• Reinstall the Drain Bolt
  • Clean the drain bolt thoroughly.
  • Thread it back in by hand, then tighten with the ratchet. Do not overtighten: snug is sufficient to prevent stripping the threads or damaging the case.
• Refill with Fresh Oil
  • Use a measuring cup to pour exactly 500 ml of 15W-50 gearbox oil into the oil filler on the right side of the engine.
  • GAS GAS recommends Motorex oil, but high-quality alternatives like AMSOIL Dominator Racing Oil are also suitable. Do not overfill–precise measurement is important for clutch and gearbox longevity.
• Check Oil Level
  • Wipe off any spilled oil and ensure the filler cap is tightened.
  • Start the bike, let it run for 30 seconds, then shut it off and let it sit for a minute. Check for leaks and verify oil level using the inspection window, if equipped.
• Clean Up
  • Dispose of used oil responsibly at your local recycling center.
  • Wipe down any drips or spills around the engine and floor to prevent slipping hazards.

Important Model-Specific Callouts for the 2021 GAS GAS MC 65

• Drain Bolt Access: The location of the oil drain bolt requires a shallow 13mm socket; using a deep socket or standard wrench may necessitate shift lever removal, which isn’t required with proper tools.
• Gearbox Capacity: 500ml (half a liter), not more or less. Excess oil can cause clutch drag, insufficient oil can cause premature wear.
• Recommended Oil: 15W-50 gear oil is generally specified. Motorex is the factory recommendation but high-performance substitutes like AMSOIL are commonly used without issue.
• O-ring Replacement: Periodically replace the drain bolt O-ring to prevent seepage. Universal O-ring kits are inexpensive and prolong engine life.
• Oil Change Interval: For heavy motocross or race use, change the oil after every 2-3 rides; less frequent changes may suffice for mild use but avoid exceeding manufacturer recommendations.

Tips for a Flawless Oil Change

• Keep a dedicated rag nearby to quickly wipe up spills. Transmission oil can be particularly messy.
• Always use a clean, dry measuring cup to ensure accurate oil volume.
• If you ride in very muddy or wet conditions, consider shortening your oil change intervals to extend the life of your clutch and gearbox.

Why Trust MotoSport.com?

This proprietary guide is tailored from years of hands-on experience and directly references factory standards and expert practices for the 2021 GAS GAS MC 65. For all your maintenance parts, oil, and riding needs, trust MotoSport.com to keep you and your bike race-ready.

Ride hard, ride smart, and let your maintenance routine power your performance.

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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.