How to Change the Coolant in a 2018 Yamaha YZ250 – MotoSport Exclusive Guide

Shop parts for a 2018 Yamaha YZ250 Dirt Bike.

Keeping your 2018 Yamaha YZ250 running at peak performance means routine maintenance—and changing the coolant is a critical step, especially before race season or after heavy usage. This step-by-step guide, created just for MotoSport customers, covers everything you need to know about changing and refilling the coolant in your YZ250, along with key insights specific to this legendary motocrosser.

What You Need

  • Fresh, high-quality coolant compatible with aluminum radiators
  • Socket set or wrenches
  • Drain pan
  • Funnel
  • Clean rags
  • Safety gloves & goggles

Preparation: Safety First

  • Ensure the bike is completely cool—hot coolant can cause serious burns.
  • Work in a ventilated area to avoid inhaling fumes.

Step 1: Remove the Skid Plate (if equipped)

The YZ250 may have an aftermarket skid plate covering the water pump. Remove it for better access to the drain bolt. Factory equipment varies, but checking for this step can save time and frustration.

Step 2: Open the Radiator Cap

With the bike fully cooled, unscrew the radiator cap to allow air in; this prevents vacuum lock and ensures complete draining.

Step 3: Locate & Remove the Drain Bolt

  • The coolant drain bolt on the YZ250 is typically on the lower side of the water pump cover—the right side of the engine.
  • Position a drain pan under the area to catch old fluid.
  • Remove the bolt and allow all coolant to drain out.
  • Quick tip: Open the small bleed bolt on the top of the cylinder head (if equipped) to speed draining and fully evacuate air pockets.

Step 4: Flush the System (Recommended)

If the coolant shows signs of contamination (rust, debris, oil), flush the system with distilled water. Fill, run the engine briefly (with cap on), shut off, and drain again. Repeat until the water runs clear. Never use tap water, as minerals can harm internal cooling passages.

Step 5: Reinstall the Drain Bolt

  • Clean and inspect the drain bolt and washer; replace if worn.
  • Reinstall and torque to OEM specification–over-tightening can crack the water pump cover.

Step 6: Add New Coolant

  • Use a funnel to pour new coolant into the radiator, filling to just below the neck.
  • If your 2018 YZ250 sees hard use or you race in extreme conditions, consider a coolant formulated for high heat—this can reduce the risk of boil-over and better protect your engine's power output.

Step 7: Remove Air Pockets

  • Tilt the bike from side to side gently, or use the bleeder bolt at the cylinder head to purge trapped air before reinstalling the cap.
  • Some minor top-off may be required as bubbles escape.

Step 8: Inspect, Test & Top Off

  • Reinstall the radiator cap securely.
  • Let the bike idle for a few minutes, keeping an eye on temperature and watching for leaks.
  • After cooling, re-check the coolant level and add if necessary.

Special Notes for the 2018 YZ250 Owner

  • This YZ250 uses an all-aluminum radiator with tight passages—ensure debris or mineral scale never enter the system.
  • Yamaha recommends checking coolant level and hoses for cracks or leaks regularly. Aging hoses can cause slow leaks and should be inspected each coolant change cycle.
  • Always dispose of old coolant safely according to local regulations—never pour into drains or onto the ground.
  • If using aftermarket high-performance radiators or guards, check for compatibility and clearance issues before reinstalling plastics or bolt-on accessories.

How Often Should You Change the Coolant?

For a 2018 Yamaha YZ250, fresh coolant is recommended at least once per year or every 40–60 engine hours—whichever comes first. More frequent changes benefit bikes used in hot, dusty, or competitive environments.

Summary: Keep Your YZ250 Cool Under Pressure

With routine coolant changes, your two-stroke powerplant stays protected against overheating and corrosion. MotoSport carries everything you need to complete the job right—from OEM drain bolt washers to premium coolants formulated for all competition conditions.

Related Shopping Categories

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Shop Radiator Hoses for a 2018 Yamaha YZ250 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.