How to Change the Coolant in a 1999 Honda CR80 Big Wheel

Shop parts for a 1999 Honda CR80RB Dirt Bike.

Proper radiator maintenance is key to keeping your 1999 Honda CR80RB Big Wheel running cool and strong. This model is known for its high-revving two-stroke engine and compact chassis–and a well-maintained cooling system is essential for reliable performance on the track or trail.

Tools & Supplies You Need

  • Fresh, high-quality ethylene glycol-based motorcycle coolant (avoid automotive coolant and always use one safe for aluminum radiators)
  • 10mm wrench or socket
  • Drain pan
  • Funnel
  • Distilled water (if you plan to flush or mix concentrate)
  • Gloves & safety glasses
  • Rags
  • New crush washer for the drain bolt (recommended for proper sealing)

Step-by-Step Coolant Change Process

  1. Cool Down & Prep: Only change the coolant when the engine is completely cool to avoid burns.
  2. Remove Plastic Shrouds: On the CR80RB, you'll need to remove the left side radiator shroud and potentially the seat and fuel tank for better access. Use a 10mm wrench to remove shroud bolts, and note the location of collars and grommets for correct reinstallation†.
  3. Open the Radiator Cap: Slowly twist off the radiator cap to let out any residual pressure.
  4. Locate the Drain Bolt: The coolant drain bolt is typically found on the water pump cover–left side, below the cylinder. Place your drain pan underneath.
  5. Drain the Old Coolant: Remove the drain bolt (and its crush washer). Let all old coolant drain into the pan. For a more thorough drain, tilt the bike gently side-to-side.
  6. Flush (Optional, Recommended): Reinstall the drain bolt loosely and fill the radiator with distilled water. Let it drain again to flush any residues. Repeat if the drained water looks dirty.
  7. Inspect System: Check hoses for cracks, check the radiator for bent fins, and inspect clamps for tightness. Replace worn parts as needed for best cooling performance.
  8. Replace the Washer and Tighten: Install a new crush washer on the drain bolt, then tighten securely (do not over-tighten).
  9. Add New Coolant: Use a funnel to fill the radiator with fresh coolant up to the filler neck. If your coolant is a concentrate, mix it with distilled water as directed–usually 50/50. Never use tap water as it can cause corrosion.
  10. Bleed the System: Start the bike with the radiator cap off and let it idle for a few minutes. Gently rock the bike side-to-side and blip the throttle to "burp" out any air bubbles. Top off coolant as needed during this step.
  11. Top Off & Inspect: Once the bubbling stops and the coolant level stabilizes, install and tighten the radiator cap. Wipe up any spills and check for leaks.
  12. Reinstall Bodywork: Replace the radiator shroud (and fuel tank/seat if removed), making sure to attach all hoses, bolts, and fasteners correctly according to your bike's layout†.
  13. Test Ride: Let the engine warm up and check coolant level again after cooling down. Add more if necessary and always monitor for leaks after the first ride.

Special Notes on the 1999 Honda CR80RB Big Wheel

  • This model uses a relatively small cooling system requiring only about 0.39 US quarts (0.37L) of coolant at change†.
  • Always use coolants specified for motorcycles. Honda or Honda-recommended products help prevent corrosion in your aluminum radiator and keep temperatures regulated.
  • Inspect the overflow tank for sediment or sludge and clean if needed–the overflow acts as a reservoir for excess fluid under pressure.
  • Because this is a high-revving, air-cooled two-stroke engine with a small-capacity radiator, regular checks are crucial to avoid overheating and top-end wear.

Consistent coolant maintenance will ensure your CR80RB runs cool no matter how hard you ride.

† Reference: CR80 95-03 Owner and Service Information

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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.