How to Change the Coolant in a 1990 KTM 250EXC: A MotoSport Guide
Shop parts for a 1990 KTM 250EXC Dirt Bike.
Keeping your 1990 KTM 250EXC running cool is crucial for performance and engine longevity. Coolant degrades over time due to high operating temperatures and contaminants, so changing it every 1 to 2 years or 40–50 hours of riding is a smart preventative step—especially on a 2-stroke like the 250EXC. Below you'll find a step-by-step procedure tailored for this classic dirt bike, along with model-specific notes every owner should know.
Tools & Supplies Needed
- Fresh coolant suitable for aluminum engines (avoid pure water—use ethylene glycol-based or a performance premixed product)
- 10mm wrench or socket
- Drain pan
- Funnel
- Clean rag
- Optional: Loctite or anti-seize for drain bolt
Step-by-Step Coolant Change Procedure
- Prepare the bike: Make sure your 250EXC is completely cool. Place the bike on a stand and ensure it is secure and level.
- Remove the radiator cap: Slowly twist the radiator cap (located atop the left radiator) to release any residual pressure. Removing the cap speeds up draining and prevents vacuum lock.
- Locate and remove the drain bolt: Look for the coolant drain bolt on the lower water pump cover, usually on the right engine case. Place your drain pan underneath, then remove the bolt with a 10mm wrench. Some models may have a copper washer—inspect for wear and replace if necessary.
- Drain the coolant: Let all coolant drain fully. For a more thorough flush, briefly tilt the bike side to side.
- Flush the system (optional but recommended): If the drained coolant is dirty, consider pouring distilled water into the radiator, temporarily replacing the drain bolt, and cycling the engine briefly. Turn the bike off, let it cool, then drain the rinse water.
- Reinstall the drain bolt: Wipe the area clean and reinstall the drain bolt. Tighten snugly, but do not overtighten (if torque specs are available, use 10 Nm/7.4 lbf ft). Replace the copper washer if present and worn.
- Refill with new coolant: Use a funnel to pour new coolant into the radiator slowly, filling just above the radiator core fins. The 1990 250EXC typically holds around 1.2 liters, but fill until you see the level near the cap base. Avoid overfilling.
- Bleed air from the system: Gently rock the bike and squeeze the radiator hoses to help release trapped bubbles. Top off as needed until the air is purged and the level remains stable.
- Reinstall the radiator cap: Securely fit the cap back on once you are confident all air is bled and the level is proper.
- Check for leaks and final level: Start the engine and let it idle until warm. Turn it off and allow it to cool completely, then check the coolant level again in the radiator—top off if needed.
Important Notes for 1990 KTM 250EXC Owners
- Radiator construction: The 1990 250EXC uses conventional welded aluminum radiators. Inspect the core and hoses for corrosion or leaks—older bikes may develop pinhole leaks along seams or hose connections over time.
- Hose condition: Original hoses may be brittle or cracked from age. Replacing them during coolant service prevents future breakdowns.
- No overflow tank: Many 1990 EXCs do not have an overflow reservoir, so watch the radiator level closely and avoid overfilling.
- Coolant type: Avoid coolant with high silicate content (common in automotive types), as this can damage the water pump seals and the aluminum core. Always use motorcycle-specific coolant or any brand that states compatibility with aluminum engines.
- Winterizing: If storing the 250EXC in freezing conditions, confirm the coolant mix provides adequate freeze protection for your climate.
- Frequent air bleeding: On these older KTMs, trapped air can lead to hot spots or overheating—if overheating persists after service, repeat the bleeding step to remove stubborn air bubbles.
Staying on top of coolant service for your 1990 KTM 250EXC keeps you riding longer and safer. For all your replacement parts, from radiators to seals and fresh silicone hoses, MotoSport offers model-specific solutions—ensuring you have exactly what you need for the next adventure.
Related Shopping Categories
Shop Radiators for a 1990 KTM 250EXC Dirt Bike.
Shop Coolant for a 1990 KTM 250EXC Dirt Bike.
Shop Temperature Sensors for a 1990 KTM 250EXC Dirt Bike.
Shop Tools for a 1990 KTM 250EXC Dirt Bike.
Shop Radiator Hoses for a 1990 KTM 250EXC 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.