How to Change the Coolant in a 1998 KTM 300EXC
Shop parts for a 1998 KTM 300EXC Dirt Bike.
Routine maintenance is key to keeping your 1998 KTM 300EXC riding at peak performance–and changing the coolant is a must for optimal engine temperature management. The 300EXC is a legendary two-stroke, renowned for its powerful delivery, light weight, and rugged simplicity, but like all high-output motocross machines, it relies on a properly bled and filled cooling system. Here's how to get the job done right on your '98 model.
Tools & Supplies You'll Need
- Fresh, motorcycle-specific coolant (1.2 liters recommended)
- Drain pan
- Socket or wrench set
- Funnel
- Clean rags
- New seal ring (recommended for drain bolt)
- Optional: Distilled water for flushing
- Bike stand (or a safe way to keep the bike upright and secure)
Drain the Old Coolant
- Ensure the engine is cool before starting. Position your KTM 300EXC upright & secure.
- Remove the radiator cap to relieve any pressure and allow for complete draining.
- Locate the coolant drain bolt on the water pump cover and position your drain pan below it.
- Remove the drain bolt. Allow all coolant to flow out into the pan. You may wish to tip the bike gently side to side for a thorough drain.
- For a more complete flush, fill the radiator with distilled water and drain again as above before final refilling.
Reinstall & Prep for Refilling
- Clean the drain bolt, install a new seal ring if available, and reinstall the bolt securely.
- Ensure the bike remains upright. For best results, slightly jack up the front end (a small height difference helps with air removal).
Fill and Bleed the Cooling System
- Slowly pour new coolant into the radiator until it's full. Use a funnel for accuracy and avoid spills.
- Locate the cylinder head bleeder bolt. Loosen it until coolant escapes without bubbles, indicating trapped air is purged. Tighten the bleeder bolt securely after bleeding.
- Refit the radiator cap.
Final Steps: Check Levels & Test Run
- Start the bike and let it idle for a few minutes with the radiator cap on to circulate coolant. Shut it off and allow the engine to cool.
- Remove the radiator cap and recheck the coolant level. Top off as needed to ensure you're at max capacity (about 1.2L).
- Inspect for any signs of leakage around the drain bolt, hoses, or radiator cap.
Specific Tips for the 1998 KTM 300EXC Owner
- The two-stroke KTM 300EXC runs hotter than many four-strokes–overheating can warp the cylinder head or damage internal components, so never skip proper bleeding.
- Check that your radiator fins are clean and unobstructed before refilling. This model's cooling capacity relies on excellent airflow.
- If you notice coolant loss over time, inspect gaskets and hoses, as two-strokes from this era may be due for replacement to prevent leaks.
- Always use high-quality coolant formulated for aluminum engines (avoid tap water only or automotive green coolant, which may not protect against corrosion in motorcycle systems).
Following these steps will keep your classic KTM 300EXC running cool, strong, and ready to tackle your next adventure on the trail or track.
Related Shopping Categories
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Shop Radiator Hoses for a 1998 KTM 300EXC 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.