How to Change the Coolant in a 1998 Suzuki RM125
Shop parts for a 1998 Suzuki RM125 Dirt Bike.
Keeping your 1998 Suzuki RM125 running cool is crucial on the track or the trail. Periodic coolant changes not only guard against overheating and corrosion but also ensure your high-revving engine gets the protection it needs. Below you’ll find a proprietary MotoSport guide tailored specifically to the 1998 RM125—including notes unique to this legendary two-stroke dirt bike.
What You’ll Need
- Fresh coolant (engineered for aluminum radiators, silicate-free recommended)
- Distilled or deionized water for flushing
- Drain pan
- 10mm socket or wrench
- Phillips screwdriver (for shrouds)
- Funnel
- Shop towels/gloves
Before You Begin
- Work when the engine is cool to the touch to avoid burns.
- Park your RM125 on level ground and secure it on a stand.
- Inspect radiator hoses and clamps–the RM125 is famous for surviving jumps and tip-overs, which can compromise hose integrity.
Step-by-Step Guide
- Remove the Shrouds:
Use your Phillips screwdriver to remove the radiator shroud bolts on both sides to access the radiators. - Locate the Radiator Cap and Drain Bolt:
Unscrew the radiator cap to release any residual pressure. Find the 10mm drain bolt on the lower part of the water pump cover—this is your coolant drain plug. - Drain the Coolant:
Place a drain pan beneath the water pump. Remove the drain bolt and let all coolant fully drain. For best results, tilt the bike gently toward the drain side. - Flush the System (Recommended):
Place the bolt back in finger-tight. Fill the radiator with distilled water. Reinstall the cap, then briefly start the bike (about 30 seconds max) to circulate the water. Turn off, remove the cap and drain the flush fluid. Repeat once as needed until water runs clear. - Refit the Drain Bolt:
After flushing, reinstall and securely tighten the drain bolt. Avoid over-tightening to prevent stripping the threads–a common pitfall in older models. - Add New Coolant:
Using a funnel, slowly pour fresh coolant into the radiator. Fill up to the base of the fill neck. - Burp the System:
Gently rock the bike side-to-side to release trapped air. Top off if needed, then re-fit the radiator cap. - Check for Leaks & Test:
Start your RM125, let it idle a few minutes, and watch for any leaks at the drain or the hose connections. Top off coolant if fluid level drops after air releases. - Reinstall the Shrouds:
Reattach both radiator shrouds, tightening all bolts securely.
1998 Suzuki RM125 Owner Tips
- The 1998 RM125 features a lightweight aluminum radiator—never use tap water for flushing, as mineral content can cause damaging deposits.
- After a coolant change, keep an eye on the fluid level during the next ride—older gaskets or hose clamps sometimes require retightening after the system warms up.
- Coolant leaks around the cylinder head or water pump may indicate gasket wear–a common issue as these bikes age. Monitor for recurring loss and inspect if required.
- Always dispose of old coolant safely–never release into the environment.
Staying on top of coolant changes for your RM125 protects your two-stroke’s performance for seasons to come. A simple flush and fill twice a year is affordable insurance for your classic Suzuki's high-revving power plant.
Related Shopping Categories
Shop Radiators for a 1998 Suzuki RM125 Dirt Bike.
Shop Coolant for a 1998 Suzuki RM125 Dirt Bike.
Shop Temperature Sensors for a 1998 Suzuki RM125 Dirt Bike.
Shop Tools for a 1998 Suzuki RM125 Dirt Bike.
Shop Radiator Hoses for a 1998 Suzuki RM125 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.