How to Change the Coolant in a 1985 Honda CR500
Shop parts for a 1985 Honda CR500 Dirt Bike.
Changing the coolant on your 1985 Honda CR500 is a crucial maintenance step to keep that big-bore two-stroke running at optimum temperature and prevent internal corrosion. This iconic model, known for its legendary power and air-cooled evolution in the Honda motocross lineup, relies on a properly maintained cooling system to deliver peak performance and longevity. Here is a proprietary MotoSport guide for a complete coolant service on your classic CR500:
What You Will Need
- Ethylene glycol-based motorcycle coolant (only use coolants safe for aluminum radiators – standard automotive antifreeze can damage the system)
- Drain pan
- Socket wrench set
- New water pump crush washer (Honda part number 90463-ML7-000 or equivalent recommended)
- Funnel
- Clean water (preferably distilled) for system flush
- Safety gloves
How to Change the Coolant
- Cool the Engine
Always perform coolant changes with the engine completely cool to prevent burns and injury. - Remove the Radiator Cap
Carefully twist off the radiator cap to relieve any pressure remaining in the system. - Locate the Coolant Drain Bolt
The CR500 uses a drain bolt on the water pump cover. Place your drain pan underneath, then remove the bolt with a socket wrench. Allow all the old coolant to fully drain out.
Consider gently leaning the bike from side to side to ensure complete draining. Take this opportunity to inspect the drained coolant for any signs of contamination or debris, which could indicate internal corrosion or gasket problems. - Flush the Cooling System
Insert the drain bolt back and temporarily refill the radiator with clean water. Replace the radiator cap, start the engine, and let it idle for a couple minutes (watch the temperature and do not let it overheat). Turn the bike off, let it cool, remove the cap, and drain again.
Repeat until the water drains out clear, ensuring you're flushing out residues and old coolant. Proper flushing is especially important on a vintage bike like the 1985 CR500 to remove sediment buildup that can restrict flow. - Reinstall the Drain Bolt
Remove the final rinse water and secure the water pump drain bolt with a new crush washer. This is essential to prevent leaks under pressure. - Refill with Fresh Coolant
Using a funnel, slowly fill the radiator neck with the recommended ethylene glycol-based coolant formulated for aluminum engines.
Fill up to the base of the radiator neck, pausing occasionally to allow air bubbles to escape. Squeeze the upper and lower radiator hoses by hand to help release trapped pockets of air. - Bleed the System
With the cap off, start the engine and let it idle. Watch for more air to bubble up and the coolant level to settle. Gradually top off if needed.
Once the coolant is steady at the correct level, replace the radiator cap securely. - Inspect for Leaks
Check around the water pump and hoses for seepage. Also, observe the overflow tube for any abnormal discharge. - Final Check
After your first short ride, let the bike cool and recheck the coolant level. Top up if necessary – slight losses can occur as any remaining air escapes.
Special Considerations for the 1985 CR500
- The 1985 CR500 is renowned for its raw power and high operating temperatures, especially during hard riding or sand tracks. Never run pure water or low-quality antifreeze, as this can cause rapid corrosion in the magnesium and aluminum cases.
- This model's radiator and cooling system were pushed hard by the engine's output. Inspect the radiator fins for clogging or damage and keep them straight for maximum airflow.
- Always use OEM-style hoses and crush washers after any disassembly to safeguard against leaks and pressure loss.
- If your CR500 has aftermarket radiators or mods, verify fill levels and bleed procedures, as designs may vary.
Regular coolant service on your CR500 preserves its durability and prevents overheating issues that can cause expensive engine repairs—especially with vintage race bikes like this legendary Honda. Keep up on your maintenance, and enjoy the unique power delivery that made the CR500 a motocross legend.
Related Shopping Categories
Shop Radiators for a 1985 Honda CR500 Dirt Bike.
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Shop Tools for a 1985 Honda CR500 Dirt Bike.
Shop Radiator Hoses for a 1985 Honda CR500 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.