How to Change the Coolant in a 1980 Kawasaki KX125: MotoSport Guide
Shop parts for a 1980 Kawasaki KX125 Dirt Bike.
Keeping your 1980 Kawasaki KX125 running cool is key to its performance and longevity. Flushing & replacing coolant should be part of your regular maintenance routine, especially if you ride hard or race. The air-cooled KX125 from this era uses a simple yet durable cooling system typical of vintage motocross bikes, but regular coolant changes will help avoid overheating and maintain optimal performance.
What You Need
- New coolant suitable for motocross bikes
- 8mm or 10mm socket – check fit on your drain bolt
- Ratchet or wrench
- Clean rag
- Drain pan to catch old coolant
- Optional: funnel for pouring new coolant
- Safety gloves – coolant is toxic
Step-by-Step Coolant Change Instructions
- Cool Off the Bike
Always start with a completely cool engine to avoid burns from hot coolant. - Locate the Radiator Cap
Remove the seat or side panel if needed for access. Twist the radiator cap off slowly to relieve any leftover pressure. - Find the Coolant Drain Bolt
Look for the drain bolt at the bottom of the water pump housing. (On the 1980 KX125, it will typically be an 8mm or 10mm bolt.)
Position your drain pan beneath the bolt. - Drain the Old Coolant
Loosen and remove the drain bolt. The old coolant will flow out – let it fully drain. For a faster, smoother drain, leave the radiator cap off.
Once flow has stopped, reinstall the drain bolt and tighten it securely, avoiding overtightening. - Fill with New Coolant
Using a funnel, carefully pour new coolant into the radiator until it reaches the fill neck.
For best results, use a motocross-specific coolant that protects against corrosion, cavitation, and extreme temps. Avoid ordinary automotive coolants with silicates, which may damage the system. - Bleed Air From System
Gently rock the bike side-to-side to release any trapped air. Add more coolant as needed to bring the level to the top.
Some bikes have a bleeder screw on the radiator. If your KX125 does, open the screw until coolant flows out without bubbles, then close. - Inspect & Test
Check the radiator cap and sealing surface for wear before installing. Clean off spilled coolant and start the bike. Allow it to idle and fully warm up, then check coolant level again.
Top off if necessary after the first ride.
Important Notes for 1980 KX125 Owners
- The 1980 KX125 was one of Kawasaki's most competitive vintage racers, using a simple, reliable cooling system that can last for decades if maintained.
- Check hoses and the radiator for leaks or corrosion when changing coolant. Parts can be tricky to find, so address any issues immediately.
- Unlike newer bikes, the 1980 KX125 lacks modern overflow bottles or temperature sensors. That makes proper coolant level & regular change intervals even more critical.
- Always dispose of old coolant responsibly at a certified collection site.
With these steps, your 1980 Kawasaki KX125 will stay at peak performance – race after race, ride after ride.
Related Shopping Categories
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Shop Radiator Hoses for a 1980 Kawasaki KX125 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.