How to Change the Coolant in a 1991 Kawasaki KX80 Big Wheel
Changing the coolant in your 1991 Kawasaki KX80 Big Wheel is a straightforward maintenance task that plays a crucial role in protecting your high-revving 2-stroke engine from overheating and corrosion. Regular coolant changes will help your bike maintain peak performance on the track or trail, especially since the KX80 BW's compact radiator is working hard to keep things cool under demanding conditions. Below, MotoSport walks you through the complete process, with key tips specific to your KX80 BW.
Preparation: What You'll Need
- Fresh motorcycle coolant (pre-mixed or to be mixed with distilled water)
- Drain pan
- Socket or wrench for the drain bolt (usually 8mm or 10mm for KX80)
- New sealing washer for the drain bolt (recommended)
- Clean funnel
- Safety gear: Gloves – coolant is toxic
- Rags for clean-up
Step 1: Cool Down & Access the System
Make sure the engine is completely cool before starting. Place the bike on a stable stand. Remove the seat and radiator shrouds if necessary for easier access to the radiator cap and fill neck.
Step 2: Drain the Old Coolant
- Place the drain pan beneath the water pump area on the right side of the engine.
- Locate and remove the coolant drain bolt – typically at the base of the water pump. Loosen the radiator cap to allow the coolant to flow freely.
- Allow all old coolant to drain out completely. Be sure to also check and drain the overflow/reservoir tank if equipped.
Step 3: Reinstall the Drain Bolt
Clean and inspect the sealing washer on the drain bolt; replace it if it's damaged or worn. Reinstall and tighten the drain bolt to factory torque spec to avoid leaks.
Step 4: Add New Coolant
- Position a funnel in the radiator fill neck.
- Slowly pour in fresh coolant – pausing every so often to let air escape and to prevent overfilling.
- If using concentrate, mix only with distilled water as minerals in tap water can damage the cooling system.
Step 5: Bleed Air from the System
Fill until the coolant reaches the bottom of the radiator fill neck. Rock the bike gently side to side to help trapped air escape. Some models may have a bleed bolt on the cylinder head; crack it open until coolant runs free if present, then retighten.
Start the bike with the radiator cap off. Let it idle for a minute or two, blipping the throttle to further burp air from the system. Check the coolant level again and top off as necessary.
Step 6: Top Up Reservoir and Reassemble
- If equipped, fill the overflow/reservoir tank up to the upper level mark.
- Install the radiator cap securely.
- Reinstall the seat and radiator shrouds.
Finishing Up
- Dispose of old coolant safely – never pour it down the drain or onto the ground.
- Record the date and engine hours or mileage for your records.
- After your first ride, recheck the coolant and top off if needed as trapped air may bleed out with engine heat.
KX80 Big Wheel Model Notes
The 1991 KX80 Big Wheel has a small-capacity radiator and tight cooling passages, making a regular coolant flush extra important for preventing blockages and overheating. Additionally, the larger wheel size places more demand on the engine, so always use a quality, premixed coolant rated for dirt bike performance. Inspect your hoses and clamps for leaks or brittleness every time you change coolant.
Keep your 1991 Kawasaki KX80 Big Wheel running cool and performing its best by staying ahead on cooling system maintenance – and trust MotoSport for the parts & gear you need for every ride.
Related Shopping Categories
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Shop Tools for a 1991 Kawasaki KX80 Big Wheel Dirt Bike.
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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.