How to Change the Coolant in a 1994 Cobra CM50

Shop parts for a 1994 Cobra CM50 Dirt Bike.

Regular coolant changes are critical to the performance & longevity of your 1994 Cobra CM50. This model's liquid-cooled engine relies on a pressurized cooling system to keep temperatures in check during aggressive riding, so following a thorough coolant service procedure is especially important. Here is MotoSport's proprietary step-by-step guide for a safe, complete coolant change.

What Makes the 1994 Cobra CM50 Unique?

  • Race-tuned two-stroke engine The CM50 features a performance-focused 50cc engine designed for competitive youth motocross.
  • High-revving cooling system demands Fast engine speeds generate extra heat, making frequent coolant inspections and changes important to prevent overheating.
  • Cobra-specific water pump and impeller design The water pump is accessed behind the stator, and the impeller should be inspected during a coolant change to ensure it is not damaged or worn.

Required Tools & Supplies

  • Allen wrenches (for radiator shrouds & drain bolts)
  • Catch pan for old coolant
  • Fresh coolant (consult manual for type; typically a 50/50 pre-mix of ethylene glycol and distilled water)
  • Distilled water for system flushing
  • Protective gloves & rags

Step-by-Step Coolant Change Instructions

  1. Prepare the Bike
    • Make sure the engine is cool to avoid burns – a warm engine can circulate coolant better during flushing, but not hot enough to cause injury.
    • Place the bike on a stable stand.
  2. Remove Radiator Cap
    • Unscrew the radiator cap slowly to relieve pressure.
  3. Drain the Old Coolant
    • Locate the coolant drain bolt, typically at the water pump housing at the bottom of the engine.
    • Position a catch pan beneath the drain point.
    • Remove the drain bolt, allowing coolant to fully escape into the pan.
    • Also remove the overflow tank if present, drain, and rinse with water. A dirty tank may need gentle scrubbing with a bottle brush.
  4. Flush the Cooling System
    • Reinstall the drain bolt and fill the radiator with distilled water.
    • Start the engine briefly (keeping a close eye on temperature), then shut off and drain again to remove any residual old coolant.
    • Repeat as needed until the drained water runs clear.
  5. Inspect Components
    • Check radiator hoses for cracks, leaks, and flexibility. Replace as needed.
    • Ensure hose clamps are tight but not over-torqued.
    • Visually inspect the impeller for wear, cracks, or damage while the system is drained.
    • Straighten any bent radiator cooling fins with a small screwdriver.
  6. Refill with New Coolant
    • Add the recommended 50/50 coolant mixture to the radiator until full.
    • Fill the overflow tank to the indicated level.
  7. Burp the System
    • Run the engine with the radiator cap off until the thermostat opens – this helps purge air pockets which can cause overheating.
    • Add coolant as needed while the engine idles, topping to keep level steady.
    • Once bubbling stops and the coolant level remains steady, reinstall the radiator cap.
  8. Final Checks & Cleanup
    • Inspect for leaks around the drain bolt, hoses, and radiator cap.
    • Dispose of old coolant properly – never dump in drains or on the ground.

MotoSport Pro Tips for the Cobra CM50

  • Always use high-quality coolant formulated for two-stroke dirt bikes to avoid premature water pump seal wear.
  • Check the cooling system after every few rides, especially if racing or riding in hot weather.
  • If you notice frequent coolant loss, inspect the water pump and stator seal – leaks can form at these points as the seals age.
  • When performing a top-end rebuild, always flush the coolant & inspect the impeller at the same time to ensure optimal engine cooling.

For OEM and upgrade replacement parts, routine maintenance, or a cooling system overhaul, MotoSport has everything you need for your 1994 Cobra CM50. Ride safe — and keep your cooling system fresh for maximum performance.

Related Shopping Categories

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Shop Temperature Sensors for a 1994 Cobra CM50 Dirt Bike.

Shop Tools for a 1994 Cobra CM50 Dirt Bike.

Shop Radiator Hoses for a 1994 Cobra CM50 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.