How to change the coolant in a 1999 Kawasaki KX250 Dirt Bike

How to Change the Coolant in a 1999 Kawasaki KX250: Step-by-Step Guide

Shop parts for a 1999 Kawasaki KX250 Dirt Bike.

Keeping your 1999 Kawasaki KX250 running cool, especially during those hard rides and track days, starts with regular coolant changes. This two-stroke motocrosser relies on efficient cooling to prevent seizures and maintain top-end power. Below is a proprietary MotoSport guide that walks you through the coolant change process with helpful tips specific to the 99 KX250.

Important Notes for KX250 Owners

• The KX250 features an aluminum engine and radiators, so always use a high-quality coolant formulated for motorcycles – avoid automotive-only coolants that can corrode aluminum components.
• This model does not use a radiator cap overflow reservoir, so filling level and system bleeding are especially important.
• Allow the engine and radiators to cool completely before starting to prevent burns and avoid cracking hot components.

What You Will Need

• New motorcycle coolant (silicate-free & safe for aluminum engines)
• Drain pan
• 8mm socket or wrench (for drain bolt)
• Phillips screwdriver
• Shop towels or rags
• Safety gear: gloves & safety glasses

Step 1: Remove the Seat & Right Side Radiator Shroud

The right side radiator drain bolt is easier to access with the seat and right radiator shroud removed. Use the correct tools to avoid stripping hardware. Place these aside for reinstallation.

Step 2: Position Your Bike & Drain the System

• Prop the bike securely on a stand.
• Place a drain pan under the right side of the engine.
• Locate the coolant drain bolt on the lower water pump cover – typically an 8mm bolt with a sealing washer.
• Remove the radiator cap slowly to relieve any pressure. Removing the cap before loosening the drain bolt allows the coolant to drain completely and smoothly.
• Unscrew the drain bolt and allow coolant to fully drain into the pan. Crack open one of the lower radiator hose clamps if needed to facilitate draining.

Step 3: Flush (Optional But Recommended)

If the coolant appears dirty or has not been changed in over a season, flushing is recommended.

• Reinstall the drain bolt finger-tight.
• Fill the system with distilled water, replace the radiator cap, start the engine, and let it run for a few minutes.
• Allow the bike to cool, then repeat the draining process. You may repeat flushing until the expelled water runs clear.

Step 4: Reinstall Drain Bolt & Add Coolant

• Ensure the drain bolt and sealing washer are clean. Torque the bolt to spec (do not overtighten, or you risk cracking the cover).
• Slowly fill the radiators with fresh coolant, tilting the bike side to side to help air escape the system.
• Fill until the coolant is just below the base of the radiator neck.

Step 5: Bleed the System

• With the radiator cap off, gently kick the engine over several times to help dislodge air ridden in the system.
• If needed, squeeze the radiator hoses carefully to work out air bubbles.
• Top off the system if the level drops after bleeding. Reinstall and secure the radiator cap.

Step 6: Reinstall Shroud & Seat

• Reattach the right radiator shroud and seat using the screws or bolts you set aside earlier.
• Double-check all connections and make sure your tools are removed from the work area.

Step 7: Final Inspection and Testing

• Start the engine and let it idle for one to two minutes. Watch the temperature and check for leaks around the drain bolt, hoses, and radiator cap.
• After your test ride, let the engine cool down and recheck the coolant level. Top off as needed.

Tips for Maximum Longevity

• Change coolant at least once per season or every 25 hours of runtime.
• Visually inspect the aluminum radiators for damage and clean out debris for efficient cooling.
• If your KX250 is raced or run in hot climates, consider a high-performance coolant for increased boiling point and corrosion resistance.
• Tighten all hose clamps securely, but do not overtighten. Kawasaki OEM parts are available for replacement if you notice worn or cracked hoses.

Changing the coolant on your 1999 Kawasaki KX250 is a straightforward task that is vital for protecting your engine during hard riding. Following the steps above will keep your cooling system in prime condition so you're ready for every throttle twist and landing.

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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.