How to Change the Coolant in a 1988 Suzuki DR125

Shop parts for a 1988 Suzuki DR125 Dirt Bike.

Keeping your 1988 Suzuki DR125 running cool is essential for performance and long engine life. Regularly replacing the coolant not only protects your motor from overheating but also prevents corrosion within the radiator and engine passages. Follow this MotoSport exclusive guide to change the coolant and keep your DR125 in top shape.

What You Will Need

  • Motorcycle-approved coolant (silicate-free for aluminum components)
  • Distilled water
  • Drain pan
  • Socket or wrench (usually 10mm or 12mm for drain bolt)
  • Screwdriver for body panel removal (if required)
  • Funnel
  • Clean rags
  • Gloves

Before You Start

  • Make sure the engine is completely cool. Opening the radiator cap while hot can cause severe burns.
  • Work in a well-ventilated area, and dispose of used coolant according to local environmental regulations.

Step 1: Access the Radiator and Coolant System

  • Remove any body panels or shrouds blocking access to the radiator and filler cap. Most panels are secured with screws or bolts.
  • Locate the radiator cap and the coolant drain bolt, typically found at the lowest point on the water pump or engine side cover.

Step 2: Drain the Old Coolant

  • Place a drain pan beneath the engine.
  • Remove the radiator cap to allow air in and help the coolant flow out smoothly.
  • Loosen and remove the drain bolt. Allow all coolant to fully drain into your pan. Some DR125s also have a small coolant reservoir tank, so check your manual and drain it if applicable (using a suction device if needed).

Step 3: Flush the System (Recommended)

  • Reinstall the drain bolt (with a new washer if possible).
  • Fill the radiator with distilled water to flush out any remaining debris or old coolant. Replace the cap and run the engine for a couple of minutes. Let it cool, then drain again.
  • Repeat the flush once more if the drained water is still cloudy or discolored.

Step 4: Add New Coolant

  • Ensure the drain bolt is reinstalled tightly.
  • Using a funnel, slowly fill the radiator with premixed coolant, or use a 50/50 mix of concentrate and distilled water as specified for the DR125 (never use tap water, which can cause mineral deposits).
  • Fill until the fluid reaches the bottom of the filler neck.
  • Top off the coolant reservoir tank to the "full" line if present.

Step 5: Bleed Air from the System

  • Leave the radiator cap off. Start the engine and let it idle. Gently rock the bike and blip the throttle a few times to help air bubbles rise out of the system.
  • As the engine warms, you may see the coolant level drop. Add more coolant if needed until it stays at the filler neck.
  • Once no more air emerges and the coolant level stabilizes, turn off the engine and allow it to cool fully.
  • Check coolant level one last time and top up if necessary. Close and secure the radiator cap.

Step 6: Inspect for Leaks & Recheck Coolant Level

  • Check under the bike and around the coolant system for leaks.
  • After your next ride, let the engine cool and check the coolant level again in both the radiator and reservoir. Air may continue to work itself out after the first few heat cycles–top off as needed.

Special Considerations for the 1988 Suzuki DR125

  • The DR125 uses an air-cooled motor with a small supplementary oil-cooling system on most trims; check your specific model for an actual radiator, as some DR125 variants may not use liquid coolant. If unsure, refer to your owner's manual or inspect the engine for coolant hoses and a radiator.
  • If your model is air-cooled only, routine cleaning of the cooling fins and regular oil changes are critical–coolant change is not required.
  • If equipped with a coolant reservoir, it is usually concealed beneath the left side panel.

Final Notes

  • Always use high-quality, motorcycle-specific coolant to prevent corrosion or damage to aluminum engine components.
  • Keep coolant away from paint and plastics, as it can damage finishes.
  • Record your maintenance date for future reference.

Related Shopping Categories

Shop Radiators for a 1988 Suzuki DR125 Dirt Bike.

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Shop Temperature Sensors for a 1988 Suzuki DR125 Dirt Bike.

Shop Tools for a 1988 Suzuki DR125 Dirt Bike.

Shop Radiator Hoses for a 1988 Suzuki DR125 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.