How to Change the Coolant in a 1979 Suzuki RM125
Shop parts for a 1979 Suzuki RM125 Dirt Bike.
Keeping your 1979 Suzuki RM125 running cool on the track or trail relies on proper maintenance of its cooling system. Changing the coolant is essential to prevent overheating and corrosion and should be done every two years or at the start of each season. Here’s your exclusive MotoSport guide to refreshing your RM125’s cooling system for long-lasting performance.
Step-by-Step Coolant Change Instructions
- Cool Down Completely
Never open the RM125 radiator cap when the engine is hot–wait until it is fully cooled to avoid injury from scalding fluid or steam. - Position Your Bike
Set the RM125 on level ground and keep it upright using a stand. - Remove the Radiator Cap
Unscrew the radiator cap firmly. Inspect the rubber gasket for cracking, and clean any dirt from the neck to prevent contamination. - Drain the Old Coolant
Locate the lower radiator hose and carefully loosen the clamp. Slide the hose off the radiator fitting, letting the coolant flow into your drain pan.
Pro tip: Use upgraded titanium hose clamps to enhance durability and corrosion resistance — this is a recommended upgrade for vintage RM125s. Titanium clamps conduct less heat, won’t rust, and offer tighter tolerances for better cooling system integrity. - Optional Flush
If your RM125 hasn’t been maintained or has evidence of corrosion, flush the system before refilling. Make a solution of 50% distilled water and 50% white vinegar. Fill and run the engine to operating temperature, then drain and flush with distilled water only. - Reconnect Lower Hose
Refit the hose securely, replacing clamps as needed (especially if original). Ensure a tight seal to avoid future leaks. - Pour New Coolant
Fill the radiator neck with a fresh 50:50 mix of high-quality engine coolant and distilled water. Do not use pure water as it lacks corrosion protection. - Remove Air
Lean the bike side to side and gently squeeze radiator hoses to encourage air bubbles to escape. - Install Radiator Cap
Tighten the -cap securely until it locks – improper installation may prevent the system from pressurizing and cause overflow issues. - Final Checks
Start the bike and let it idle for a few minutes. Shut off and let cool. Recheck level; the coolant should sit at the bottom of the radiator inlet hole.
Note: The 1979 RM125 does not have an overflow tank, so coolant levels may drop during hard riding or after shutdown. Always check coolant before each ride.
Model-Specific Notes for the 1979 Suzuki RM125
- No Overflow Tank
Unlike newer bikes, your RM125 doesn’t have a dedicated overflow reservoir. Losses are expected, especially during aggressive riding. - Watch for Gasket Wear
Original radiator caps and hoses may have deteriorated – consider replacing these with modern alternatives for reliability. - Improved Cooling Options
Upgraded titanium hose clamps dissipate less heat and reduce weight a performance and longevity boost for your vintage Suzuki.
Tips for Longevity
- Inspect coolant color frequently; milky or oily residue means further engine attention is needed.
- Always use the correct coolant mix and check levels before riding.
- Store your bike in a cool, dry space to prevent rubber hose aging and internal corrosion.
MotoSport is your destination for expert parts and upgrades for the legendary 1979 Suzuki RM125. Confidently perform routine coolant changes, and enjoy more laps with less worry about overheating.
Related Shopping Categories
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Shop Radiator Hoses for a 1979 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.