How to Change the Coolant in a 2012 Cobra CX50SR

Shop parts for a 2012 Cobra CX50SR Dirt Bike.

Routine coolant changes are essential for the performance and longevity of your 2012 Cobra CX50SR. Proper maintenance prevents overheating and protects internal engine components, which is especially important for high-revving mini motocross bikes like the CX50SR. Here is a model-specific, step-by-step guide exclusively for MotoSport riders.

Tools & Supplies Needed

  • Phillips or flathead screwdriver (for plastic removal if needed)
  • Appropriate socket/wrench (to remove drain bolt)
  • Drain pan
  • Funnel
  • New coolant compatible with motocross 2-strokes
  • Distilled water (if mixing coolant)
  • Clean shop rags
  • Safety gloves and eye protection

Step 1 – Preparation

  • Ensure the bike is on a level stand and engine is cool before beginning.
  • For easier access, remove any plastics or body panels near the radiator if needed.

Step 2 – Draining the Old Coolant

  • Locate the radiator cap and slowly remove it to release system pressure.
  • Find the coolant drain bolt – typically located on the lower part of the water pump or at the base of the engine case. Place the drain pan under it.
  • Remove the drain bolt and allow old coolant to completely drain into the pan.
  • If coolant appears dirty or contains debris, consider back flushing the system with distilled water before refilling. (If your bike has experienced impeller failure, flushing is required before reassembly.)
  • Inspect and clean the drain bolt and its gasket, replacing if worn. Reinstall and tighten after draining is complete.

Step 3 – Refilling with New Coolant

  • Use coolant formulated for motocross engines. If concentrated, pre-mix using distilled water according to the label instructions – typically a 50/50 ratio.
  • Pour new coolant slowly into the radiator through a funnel until it reaches the bottom of the radiator filler neck. Fill any overflow reservoir to the recommended level.

Step 4 – Removing Air from the System

  • Leave the radiator cap off and start the engine. Let it idle briefly, gently rocking the bike side-to-side to encourage air bubbles to escape.
  • Watch for air bubbles emerging from the filler neck; top off as needed until the bubbles stop and the level remains constant.
  • Once the cooling system is free of air, reinstall the radiator cap.

Step 5 – Final Checks

  • Run the engine up to operating temperature and then turn it off. Let it cool fully – recheck the radiator and overflow reservoir, topping off as needed.
  • Examine under the bike for leaks at all connections and drain plugs.
  • Reinstall plastics and clean up any spilled coolant immediately. Used coolant should be disposed of at a proper recycling center.

Notes for Cobra CX50SR Owners

  • Coolant Loss During Break-In: It is normal to lose up to 4 oz (120 ml) of coolant via the overflow hose during engine break-in. Monitor the level closely during the first ride and top off as needed.
  • Clutch & Engine Heat: Prolonged, aggressive riding can generate significant heat. Consider allowing the ignition system to cool with the cover off after hard rides—this helps preserve the stator and other heat-sensitive components.
  • Regular Inspection: Check the radiator and hoses for signs of leaks or damage every ride, especially after changing coolant or during hot conditions.
  • Air in the System: Always ensure air is fully burped out of the radiator before riding. Air pockets can cause overheating and engine damage.

Keeping your Cobra CX50SR's cooling system in peak condition is key to reliable performance on and off the track. Trust MotoSport.com for all your maintenance parts and expert advice.

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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.