How to Change the Coolant in a 2009 Cobra CX50SR

Shop parts for your ride now.

Maintaining your 2009 Cobra CX50SR is essential for top performance – one crucial task is regularly changing your coolant. The CX50SR is a purpose-built competition mini motocrosser with a high-revving engine and a compact yet efficient liquid cooling system. Because the engine works harder than most, proper coolant maintenance protects against overheating and engine wear.

Why Change the Coolant?

Coolant doesn’t just control temperature. It also inhibits corrosion, lubricates the water pump, and prevents scale build-up inside the radiator and engine. Over time, heat cycles and impurities weaken these protective properties. For a competition model like the CX50SR, fresh coolant is especially important for repeated heat cycles and high engine loads.

What You’ll Need

  • Fresh, high-quality motorcycle coolant (pre-mixed or mix with distilled water as instructed on the bottle)
  • Drain pan
  • Basic hand tools (to remove radiator cap and drain bolt/plug)
  • Funnel
  • Shop towels
  • Protective gloves and eyewear

Step-by-Step Coolant Change Guide

  1. Prepare the Bike
    Ensure the CX50SR is cool to the touch before starting. Place the bike on a level stand and remove the seat and any shrouds blocking radiator access.
  2. Drain the Old Coolant
    Locate the radiator cap – remove it slowly to relieve any residual pressure. Place your drain pan beneath the water pump or drain bolt (typically found at the base of the engine). Remove the bolt and allow all old coolant to drain out fully. Inspect the drained fluid for debris, oil, or rust.
  3. Flush (Optional but Recommended)
    If the drained coolant is especially dirty, consider adding distilled water, reinstalling the drain bolt, and running the engine for a short period before draining again. This flushes old residue from the system. For competition bikes like the CX50SR, a full flush is recommended if regular maintenance has lapsed or the bike has run especially hot.
  4. Inspect Components
    While the system is empty, check radiator hoses, clamps, and the water pump for leaks or wear. The CX50SR’s impeller is a known weak point when subjected to heavy racing – ensure it is intact and spins freely. If the impeller is damaged, back flush the system before continuing.*
  5. Refill with New Coolant
    Reinstall the drain bolt securely. Using your funnel, fill the radiator slowly with fresh coolant to the base of the filler neck. Avoid overfilling. If your coolant isn’t pre-mixed, make sure to use distilled water only – never tap water – to prevent mineral buildup.
  6. Burp the Cooling System
    Air pockets can cause hotspots and overheating. With the radiator cap off, start the CX50SR and let it idle for several minutes. Gently rev the engine and lean the bike side to side to help trapped air escape. Once the level drops, add more coolant until the radiator is full.
  7. Re-check Levels and Inspect for Leaks
    Let the engine cool completely. Re-check coolant levels once more and top off if needed. Reinstall the radiator cap tightly. Check all hose connections and fittings for leaks.
  8. Dispose of Old Coolant Properly
    Used coolant is hazardous – never dump it. Store it in a sealed container and take it to your local hazardous waste center for disposal.

CX50SR Owner’s Tips & Product Notes

  • The CX50SR features a small-capacity cooling system, so fill volume is low – monitor fluid levels closely after initial start-up and heat cycling.
  • If your radiator seems to lose coolant repeatedly or overheats, check for a damaged water pump impeller as this is a known failure point on this model. Back flushing is especially important if the impeller fails.*
  • Always use a coolant compatible with aluminum systems. Avoid tap water—use only distilled for mixing.
  • The CX50SR is engineered for racing; routine maintenance is key. Replace coolant at least once per season, especially if racing in hot or muddy conditions.

MotoSport.com is dedicated to helping you keep your Cobra CX50SR at peak performance with the best OEM and aftermarket parts. If questions arise during your maintenance, our team is here to help fellow riders get the right solutions.

<.-- Superscript * above references to confirm the importance of inspecting and flushing after impeller failure, per the OEM manual for this model. -->

Related Shopping Categories

Shop Radiators for a 2009 Cobra CX50SR Dirt Bike.

Shop Coolant for a 2009 Cobra CX50SR Dirt Bike.

Shop Temperature Sensors for a 2009 Cobra CX50SR Dirt Bike.

Shop Tools for a 2009 Cobra CX50SR Dirt Bike.

Shop Radiator Hoses for a 2009 Cobra CX50SR 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.