How to Change the Coolant in a 2021 Honda CRF125F
Shop parts for a 2021 Honda CRF125F Dirt Bike.
Changing the coolant in your 2021 Honda CRF125F is a straightforward maintenance task that keeps your dirt bike running at the right temperature and extends engine life. This proprietary MotoSport guide gives you model-specific instructions plus owner tips to make the job easy and safe.
Things of Note for the 2021 CRF125F Owner
- Engine Cooling System: The CRF125F uses a closed liquid cooling system. It's important to check both the radiator and the reservoir levels after a coolant change to avoid overheating issues.
- Plastic Panels: Some covers must be removed before accessing the radiator cap or hoses, specifically the left side cover. This is secured with bolts and a prong system–refer to the steps below to avoid breaking panel tabs or grommets.
- Coolant Spec: Always use high-quality motorcycle coolant suitable for aluminum engines and radiators. Avoid mixing different coolant types.
Tools & Supplies Needed
- Phillips screwdriver and a socket set
- Drain pan or suitable container
- New coolant (Honda GN4 or equivalent for aluminum engines)
- Distilled water (if flushing)
- Clean shop towels or rags
Step-by-Step Coolant Change Guide
-
Prep the Bike
Ensure the engine is completely cool before starting. Place the bike on a stable surface or stand. -
Remove the Left Side Cover
Remove bolt A, bolt B, and the collar from the left side cover.
Gently pull the prong out of the rubber grommet, then pull the boss from the shroud's hole. Take care when removing the cover to prevent breaking any plastic tabs or damaging grommets.
(For reinstallation, align everything carefully and secure both bolts firmly.) -
Access the Radiator
Locate the radiator cap (usually found on top of the radiator on the right side, but some models place it under side panels). Remove the cap slowly to relieve any pressure. -
Drain the Old Coolant
Place your drain pan beneath the water pump or the coolant drain bolt, which is typically positioned on the lower side of the engine case. Remove this drain bolt and its copper washer, letting coolant flow completely out.
Open the radiator cap fully – this relieves vacuum pressure and ensures full drainage. -
Flush the System (Optional)
If desired, flush with distilled water. Pour water in through the radiator, re-install the drain bolt, start the engine for a minute, then repeat the drain. This step is useful if past coolant was dirty or you are switching coolant types. -
Replace the Drain Bolt
Inspect the drain bolt washer–replace if crushed or worn. Tighten the drain bolt securely but avoid overtightening as the aluminum threads can strip. -
Add New Coolant
Slowly pour in coolant directly into the radiator until full. Squeeze the radiator hose gently several times to help dislodge any trapped air bubbles.
Fill the reservoir tank to the specified "Full" mark if equipped. -
Bleed Air from System
With the radiator cap off, briefly start the engine and let it idle for a few minutes. This helps remove air bubbles. Top off the radiator as needed.
Once bubbles stop appearing and the level is steady, shut off the engine and let it cool completely. -
Recheck Levels and Reassemble Panels
Once fully cool, recheck the radiator and reservoir levels. Top off if necessary. Carefully reinstall the left side cover, ensuring all bolts, prongs, and rubber grommets are secure. -
Dispose of Old Coolant Properly
Take used coolant to a suitable hazardous waste disposal facility; never pour it down the drain or onto the ground.
Additional CRF125F Model Tips
- The CRF125F does not use a radiator fan, so maintaining proper coolant levels is especially important during slow riding or in hot climates.
- Inspect all hoses for leaks and clamps for tightness during your service.
- Check your owner's manual for the recommended coolant capacity and change interval–usually every two years for typical riding conditions.
Related Shopping Categories
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Shop Tools for a 2021 Honda CRF125F Dirt Bike.
Shop Radiator Hoses for a 2021 Honda CRF125F 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.