How to Change the Coolant in a 2025 GAS GAS MC 125: A Complete Owner's Guide
Keeping your 2025 GAS GAS MC 125 in prime condition means regular coolant changes to prevent overheating and ensure long engine life. The MC 125's advanced two-stroke design manages significant thermal loads, and its cooling system needs periodic service, especially if you race or ride in challenging conditions. This guide walks you through every step, noting what makes the MC 125 unique compared to other dirt bikes.
What You Need
- Fresh, manufacturer-approved coolant (check the owner's manual for recommended specification)
- Drain pan
- Phillips screwdriver (for panels if needed)
- 8mm and 10mm sockets or wrenches
- Rags
- Safety gloves and eye protection
Steps to Change the Coolant on a 2025 GAS GAS MC 125
- Ensure engine is cool. Never open the radiator cap on a hot engine–scalding coolant and steam can cause serious burns.
- Remove the right side panel. If working space is tight, remove the right side panel using a Phillips screwdriver for easier access to the radiator and hoses.
- Position your drain pan. Place a drain pan under the right side of the engine, beneath the water pump drain bolt (typically the lowest bolt on the coolant pump cover).
- Open the radiator cap. Slowly loosen the radiator cap to relieve system pressure.
- Remove the water pump drain bolt. Use the correct socket to remove the bolt and allow coolant to fully drain into the pan.
- Inspect coolant. Look for debris or oil (a milky color can indicate engine gasket issues).
- Flush system if needed. If your old coolant is dirty or you're switching coolant type, flush with distilled water. Replace the drain bolt and torque to manufacturer specs (see your owner's manual).
- Refill with new coolant. Fill the radiator slowly, pouring until coolant reaches the top of the fill neck. The MC 125 features a bleeder screw on or near the cylinder head–after filling, crack this slightly to vent trapped air until only coolant drips from the screw, then retighten.
- Burp the system. Briefly start the engine with the radiator cap removed and let it idle. Gently rock the bike or lightly blip the throttle. Watch for disappearing bubbles–indicates air is leaving. Shut engine off and top up coolant level as needed.
- Replace radiator cap and reassemble panels. Confirm coolants at the correct level and reattach any panels removed.
- Check for leaks. Start the bike, bring it to operating temperature, and inspect the drain bolt and hose connections for any signs of leaks.
Special Notes for the 2025 GAS GAS MC 125
- Coolant Type: Only use coolant specified for aluminum engines and never mix types (ethylene glycol, propylene glycol, waterless, etc.). Always dilute concentrate with distilled water as tap water can cause scale and internal corrosion.
- Bleeder Screw: The MC 125's cylinder head bleeder screw is essential for removing trapped air–skipping this step can lead to air pockets and overheating.
- Capacity: Reference your owner's manual for precise system capacity and torque specs for the drain bolt and bleed screw.
- Fan Kit Compatibility: Racing in hot climates? Installing a radiator fan kit is advised for sustained slow-speed or technical riding.
- Disposal: Used coolant is toxic. Always dispose of it at a certified recycling or waste collection facility.
Final Tip
Check coolant condition at least every other oil change or before any big ride. Sticking to the factory cooling system maintenance schedule keeps your MC 125 performing at its best in all conditions–on the MX track or trail.
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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.