How to Change the Coolant in a 1979 Suzuki RM250
Shop parts for a 1979 Suzuki RM250 Dirt Bike.
Owning a vintage 1979 Suzuki RM250 is a unique experience—these bikes are renowned for their lightweight frames, powerful two-stroke engines, and legendary MX heritage. Regular maintenance, particularly a coolant change, keeps the RM250 running strong and prevents costly overheating issues. Here’s an exclusive MotoSport.com guide, tailored for your classic bike and packed with tips you won’t find elsewhere.
Supplies You’ll Need
- Fresh engine coolant (premixed or mix with distilled water; avoid tap water due to mineral contamination)
- Catches pan or drain tray
- Socket set–you’ll need an 8mm socket for the drain bolt
- Rags and safety gloves
Preparation
- Let the engine cool completely before starting to prevent injury from hot coolant or pressurized vapor.
- Place your RM250 on a stable stand in a well-ventilated and clean workspace.
- Remove the seat and tank shrouds if needed for easy access to the radiator. This model typically lacks an overflow tank, so prepare accordingly.
Step-by-Step Coolant Change
- Open the Radiator Cap
Carefully remove the radiator cap. Do not attempt this when the engine is hot to avoid scalding injury. - Locate and Remove the Drain Bolt
The 1979 RM250 features a small drain bolt at the base of the water pump. Place your catch pan underneath and remove the bolt with your socket. Allow all coolant to fully drain. For a thorough flush, slowly pour distilled water through the radiator to help remove lingering debris and old coolant. - Inspect & Replace Gasket Washer
If the drain bolt washer is damaged or old, replace it. This prevents leaks and helps maintain system pressure. - Reinstall Drain Bolt
Clean the bolt threads, then reinstall and hand-tighten, followed by torquing to approximately 11 N·m (8 lbf-ft). - Refill with Fresh Coolant
Patiently pour coolant up to the neck of the radiator filler. The RM250’s coolant capacity is around 950 ml. Do not overfill. - Air Bleeding
With the cap still off, gently rock the bike side-to-side and slowly squeeze the coolant hoses to help release any trapped air. Some models feature an air bleeder bolt–if present, briefly loosen this while topping up coolant, then tighten securely. - Secure the Radiator Cap
Once the coolant is steady at the filler neck with no visible air, reinstall and tighten the radiator cap.
Final Check
- Start the engine and let it idle. Monitor the temperature and inspect the system for leaks.
- After a few minutes, shut the bike off and let it cool completely before rechecking the coolant level. Top off if necessary.
RM250-Specific Tips
- No Overflow Tank: Check coolant often; this generation bleeds excess through a breather tube with no external reservoir, meaning rapid losses can indicate a problem.
- Rider Era Design: The radiator is exposed. Be gentle when loosening and tightening old components–original parts may be brittle after decades of riding.
- Routine Inspection: Check radiator fins for damage and ensure hoses are soft and crack-free. Replace any weak hoses–they’re easy to overlook but critical for durability.
Keep your legendary RM250 at its peak by making coolant checks and changes part of your regular maintenance schedule. Thoughtful care now preserves the exciting power and classic feel that defines your Suzuki, both on and off the track.
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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.