How to Change the Coolant in a 1988 Suzuki RM250

Shop parts for a 1988 Suzuki RM250 Dirt Bike.

Regularly changing the coolant is crucial to keep your 1988 Suzuki RM250 running strong, prevent overheating, and protect the engine from costly damage. The RM250 is a classic 2-stroke motocross bike, making good cooling performance especially important for high-RPM, off-road riding. Follow this MotoSport.com proprietary guide to change the coolant on your RM250 with confidence.

What You’ll Need

  • Correct engine coolant (check your manual for compatibility – most prefer ethylene glycol-based coolant for vintage 2-strokes)
  • Socket set & wrenches
  • Drip pan
  • New drain bolt washer (recommended for proper sealing)
  • Funnel and clean rags
  • Gloves & eye protection

Step-by-Step Coolant Change

  1. Prep the Bike: Make sure the engine is cool. Set the bike upright on a stand. Clean the radiator cap area to prevent debris from falling in.
  2. Remove the Radiator Cap: Slowly open the radiator cap to release system pressure. Never do this on a hot engine to avoid burns.
  3. Locate & Remove the Drain Bolt: The drain bolt is usually found on the lower side of the water pump cover. Position the drip pan underneath and remove the bolt. Let all old coolant drain out fully. Replace the old washer with a new one for leak-free sealing.
  4. Reinstall the Drain Bolt: Tighten the bolt to 11 N·m (8.0 lbf-ft) for proper torque and to prevent overtightening leaks.
  5. Flush the System (Optional but Recommended): If the coolant was heavily contaminated, run distilled water through the system, drain, and repeat until clear. For a full flush, remove lower radiator hoses and carefully use compressed air to blow out residue.
  6. Fill with Fresh Coolant: Using a funnel, slowly pour the specified coolant into the radiator. The RM250 holds approximately 950 ml (1.0 US quart) of coolant. Fill only to the base of the filler neck to allow for expansion.
  7. Bleed Air from the System: Temporarily loosen the air bleeder bolt on the top of the radiator (if present). Add coolant until it seeps from the bleeder – tighten the bolt to 6 N·m (4.5 lbf-ft). This removes trapped air, which can cause overheating.
  8. Burst/Burp the System: Briefly start the engine with the radiator cap off. Let it idle for a minute to circulate coolant and release air bubbles. Stop the engine and top off if necessary. Replace the radiator cap securely.
  9. Check for Leaks: Double-check all fittings, bolts, and the drain plug area. Correct torque is key to prevent weeping or leaks.
  10. Final Verification: After a short test ride, recheck coolant level and look for any drops in the catch pan or seepage around hoses, clamps, and the drain bolt.

Special Considerations for the 1988 Suzuki RM250

  • The 1988 RM250 features aluminum radiators and a relatively small total coolant volume. Overfilling makes pressure leaks more likely, and underfilling increases the risk of overheating. Aim for the correct level.
  • Inspect rubber radiator hoses for aging or cracking. This era of RM can suffer from swollen or brittle hoses – replace as needed to prevent trackside breakdowns.
  • The bike’s high-revving, 2-stroke engine generates significant heat. Regular coolant changes (every year or 20-30 riding hours) are highly recommended, especially if you ride aggressively, in sand, or in hot conditions.
  • Never mix coolant types – always completely drain and flush before switching formulas. Using the wrong mix can cause corrosion, scale, or poor cooling efficiency.

Disposal — Do It Right

Always properly dispose of old coolant. Never pour it down drains or on the ground. Take it to an authorized recycling center or auto parts store that accepts coolant waste.

Keep Your RM250 at Peak Performance

Changing the coolant is a simple service that protects your classic RM250 from catastrophic overheating and keeps your ride ready for the next moto. Proper cooling is just as important as air filter cleaning and regular oil changes for long engine life.

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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.