How to Change the Coolant in a 1987 Yamaha YZ80 – Step-by-Step Guide

Shop parts for a 1987 Yamaha YZ80 Dirt Bike.

Keeping your 1987 Yamaha YZ80 in top shape means regular maintenance – and few jobs are as critical as changing your coolant. A fresh coolant flush prevents overheating, protects your aluminum engine, and ensures reliable performance whether you're hitting the track or trails. This guide from MotoSport.com walks you through the coolant change process, highlighting key tips specific to the legendary YZ80.

What You'll Need

  • High-quality ethylene glycol-based coolant designed for aluminum engines
  • Distilled or soft water (for mixing if not premixed)
  • Socket set and Phillips screwdrivers
  • Catch pan/container for old coolant
  • Rags or shop towels
  • Protective gloves

Step 1: Prepare the Bike

  • Place the bike on a stable stand and ensure the engine is cool to avoid burns.
  • Remove the seat and side panels if needed for easier radiator access.

Step 2: Drain the Old Coolant

  • Locate the coolant drain bolt on the water pump cover (typically at the lowest point), and place your drain pan underneath.
  • Slowly remove the radiator cap to release any pressure in the system.
  • Remove the drain bolt and let the old coolant fully drain out.

Step 3: Flush the Cooling System (Recommended)

  • Replace the drain bolt temporarily and fill the radiator with distilled water.
  • Reinstall the cap, start the engine, and run for a minute to help flush debris and remaining coolant.
  • Let the engine cool, then drain again by removing the bolt and radiator cap.

Step 4: Reinstall the Drain Bolt

  • Inspect the copper washer on the drain bolt for wear; replace if necessary to prevent leaks.
  • Reinstall and tighten the drain bolt securely (approx. 10 Nm or 7.2 ft–lb).

Step 5: Fill with New Coolant

  • Mix your coolant and distilled water at a 50/50 ratio if not using premixed coolant. The YZ80 requires about 0.95 liters total capacity.
  • Pour slow and steady into the radiator neck, allowing bubbles to escape and maximizing air purging.

Step 6: Bleed Air from the System

  • With the radiator cap off, gently rock the bike side-to-side to release trapped air pockets.
  • Top off to the base of the filler neck, then reinstall the radiator cap.
  • Start the engine and let it heat up to operating temperature – this helps purge remaining air. Watch for coolant expansion and check for leaks around the drain bolt and hoses.
  • Cool the engine fully, then recheck and top off the coolant as needed. Reinspect the reservoir and radiator level after a test ride to ensure they're full; repeat as necessary if levels drop slightly.

YZ80-Specific Notes

  • The 1987 Yamaha YZ80 features an aluminum cylinder and head, so use only coolant safe for aluminum components to avoid corrosion.
  • Pay close attention to the condition of the rubber O-rings and gaskets at the water pump and radiator cap – leaks here are common on vintage YZ models. Replace if signs of deterioration are present for maximum longevity.
  • If you notice repeated coolant loss or milky coolant, inspect the water pump seal and clutch cover gasket, as they are known maintenance points on YZ80s of this era.

Dispose of Old Coolant Responsibly

  • Used coolant is toxic. Take it to an approved recycling or hazardous waste center.

The 1987 YZ80 is a true classic—give it the care it deserves so it keeps running strong. For all replacement gaskets, radiators, caps, and high-performance coolant, MotoSport has you covered for every vintage ride.

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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.