How to Change the Coolant in a 2019 Cobra CX50JR

Shop parts for a 2019 Cobra CX50JR Dirt Bike.

Keeping the cooling system in top shape is vital to protect your 2019 Cobra CX50JR engine and maximize performance. This MotoSport proprietary guide walks you through a thorough coolant change specifically for this dirt bike, covering unique model notes and expert tips to help you keep your Cobra running strong.

Tools – What You Need

  • Flat head screwdriver
  • Appropriate metric hex keys (up to 8mm)
  • Drain pan
  • Fresh pre-mixed motorcycle coolant (preferably suitable for high-performance 2-stroke engines)
  • Distilled water (for flushing)
  • Clean rags

Preparation – Safety First

  • Only perform coolant service when the engine is cool – hot coolant can cause burns.
  • Work in a well-ventilated area with the bike securely supported on a stand.

Step 1: Remove the Radiator Cap – Inspect Coolant

  • Locate the radiator cap and carefully remove it. Inspect the coolant for oil residue or black debris, which might indicate internal engine issues. If you notice anything abnormal, schedule a deeper inspection before refilling.

Step 2: Drain the Old Coolant

  • Place a drain pan beneath the bike.
  • Loosen and remove the drain plug or lower radiator hose. Allow all coolant to escape completely.
  • If your coolant shows signs of contamination or the water pump impeller is damaged, consider flushing the system with distilled water – back-flushing can help remove solid particles.

Step 3: Flush (Optional but Recommended)

  • If the system is dirty, fill the radiator with distilled water and run the engine briefly, then drain again. This minimizes contaminant build-up.

Step 4: Reinstall Plug – Add New Coolant

  • Replace the drain plug securely.
  • Pour fresh, pre-mixed coolant into the radiator until it covers the top of the cores. Avoid using tap water – distilled water prevents mineral deposits.

Step 5: Burp the Cooling System

  • Start the engine with the radiator cap off. Run it at idle and gently blip the throttle. Rock the bike side-to-side to help purge trapped air.
  • Once the fluid level drops, top it up to the filler neck. When air is removed, install the radiator cap.

Step 6: Heat Cycle – Recheck

  • Run the bike until fully warm so the thermostat opens, helping circulate and expand coolant. After shutting down, wait for the bike to cool to ambient temperature. Recheck the coolant level – it should be at the base of the filler neck. Loss of up to 4 oz (120 ml) is normal as air escapes the system. Top off if needed.

Step 7: Coolant Reservoir – Final Check

  • If equipped, inspect and top off the coolant reservoir. Only check and add coolant with the bike fully cold to avoid dangerous spray from hot pressurized fluid.

Notes – Cobra CX50JR Details

  • This model's cooling system relies on a compact radiator and high-flow water pump. Any impeller damage must be addressed before filling – running with a compromised pump will quickly lead to overheating.
  • Always use a quality, high-performance 2-stroke compatible coolant; Cobra recommends keeping the coolant level just above the radiator cores.
  • Regular coolant service is essential since stator failure, common on this model, can be triggered by running the bike hot due to low or contaminated coolant.
  • Dispose of old coolant responsibly at an appropriate recycling center.

Pro Tip – About Coolant Levels

  • Minor losses after refill and heat cycling are expected as the system self-bleeds remaining air. Persistent loss means you may have a leak or another issue.

Optimal performance requires scheduled maintenance: change your coolant at least once a year or after severe riding conditions. Your 2019 Cobra CX50JR deserves the bestwhen it comes to parts or fluids, trust MotoSport to help keep your ride in peak condition.

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Shop Radiator Hoses for a 2019 Cobra CX50JR 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.