How to Change the Coolant in a 2021 Honda CRF125FB
Shop parts for a 2021 Honda CRF125FB Dirt Bike.
Maintaining the cooling system of your 2021 Honda CRF125FB is essential for reliable performance on the trail or track. Fortunately, changing the coolant on this dirt bike is a straightforward task that you can handle in your own garage with a few basic tools and a little preparation. The following guide will walk you through the process and highlight key tips specific to your CRF125FB.
What You Need
- Silicate-free motorcycle coolant compatible with aluminum radiators (OEM or high-quality aftermarket)
- 5mm Allen wrench (for plastics)
- 8mm and 10mm sockets with ratchet (for bolts)
- Funnel
- Catching pan for old coolant
- Paper towels or rags
- Phillips screwdriver
- New crush washer for the drain bolt (recommended)
Changing the Coolant–Step by Step
- Ensure the bike is cool. Never open the radiator cap or drain coolant when the engine is hot. Wait for the CRF125FB to cool completely.
- Remove the right side radiator shroud. Using the 5mm Allen wrench, remove the bolts securing the right-side plastic shroud to access the radiator cap.
- Place a drain pan under the water pump area. Look for the drain bolt (typically positioned at the lowest point of the water pump). Loosen the bolt with an 8mm or 10mm socket and allow all coolant to drain out.
- Remove the radiator cap. Use a Phillips screwdriver if your cap is covered by a retaining screw. Removing the cap allows the coolant to drain quickly and completely.
- Inspect the old coolant. Check for debris or discoloration. If you see sludge or particles, consider rinsing the system with distilled water before adding new coolant.
- Replace the drain bolt (preferably with a new crush washer). Torque to spec, being careful not to overtighten.
- Fill the radiator slowly with the new coolant. Pour until the fluid reaches just below the neck of the radiator filler.
- Bleed the system. Briefly rock the bike side to side and gently tap the hoses to help release any trapped air bubbles. Wait a few minutes for the coolant level to settle, then top off as needed.
- Reinstall the radiator cap and side shroud. Make sure the cap is tight, and reinstall all plastics and hardware.
- Start the engine and let it run briefly. After a few minutes, shut it down and let the bike cool. Recheck the coolant level and add more if necessary. Top off the overflow reservoir to the correct mark if equipped.
Key Notes for CRF125FB Owners
- The 2021 CRF125FB uses aluminum components that are best protected by silicate-free coolant specifically intended for modern dirt bikes.
- Routine maintenance–coolant changes every two years or 50 hours of riding–will keep overheating and corrosion at bay, especially during extended trail riding or in hot climates.
- Always dispose of old coolant properly—never pour it down household drains or onto the ground.
- Inspect radiator hoses and clamps for signs of leaks or aging during the process. Replace as needed to ensure a sealed cooling system.
Regular coolant changes will extend the life of your CRF125FB's engine and make sure every ride is a great one. Remember, always refer to your owner's manual for torque specs and cooling system capacity unique to your machine.
Related Shopping Categories
Shop Radiators for a 2021 Honda CRF125FB Dirt Bike.
Shop Coolant for a 2021 Honda CRF125FB Dirt Bike.
Shop Temperature Sensors for a 2021 Honda CRF125FB Dirt Bike.
Shop Tools for a 2021 Honda CRF125FB Dirt Bike.
Shop Radiator Hoses for a 2021 Honda CRF125FB 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.