How to Change the Coolant in a 1997 Cobra BM50: Essential Tips – MotoSport Exclusive
Shop parts for a 1997 Cobra BM50 Dirt Bike.
Keeping your 1997 Cobra BM50 running cool is key for lasting engine performance on the track and trail. This proprietary MotoSport guide details every step to safely change the coolant on your BM50, with model-specific advice every owner needs.
What Makes the 1997 Cobra BM50 Unique?
- Race-specific engine design: The BM50 features a high-revving, liquid-cooled two-stroke engine built for competition use.
- Small radiator and low coolant capacity: With only about 450-500ml in the system, prompt and correct filling is critical to prevent overheating or engine damage.
- No overflow or recovery tank: Always pay attention to proper bleeding and burping, since trapped air pockets are common in compact, race-oriented cooling circuits.
What You'll Need
- Fresh premium engine coolant (make sure it's compatible with aluminum engine components & safe for motocross bikes)
- Distilled water for flushing (optional but recommended)
- Funnel or squeeze bottle
- Drain pan
- Gloves & eye protection
- Basic hand tools
Step-by-Step Coolant Change Procedure
- Prep Your Bike
- Park the Cobra BM50 on a stable stand or flat surface.
- Let the engine cool completely to avoid burns.
- Drain Old Coolant
- Locate and remove the radiator cap slowly to release residual pressure.
- Find the cooling system drain bolt (usually on either the water pump or lower radiator hose where it connects to the engine case).
- Set a pan under the bike and remove the bolt or hose clamp to fully drain old coolant.
- Gently lean the bike from side to side to evacuate all fluid.
- If desired, flush the system by reinstalling the drain plug, filling with distilled water, running the engine briefly, then draining again.
- Inspect Key Components
- Check the radiator cap's rubber seal for wear.
- Inspect hoses for cracks or swelling. Replace any suspect parts before refilling.
- On the BM50, ensure there are no coolant leaks at the water pump or cylinder fittings.
- Refill with Fresh Coolant
- Use a funnel to pour new coolant into the radiator slowly.
- Fill until fluid reaches the bottom of the fill neck.
- Stop occasionally and gently squeeze coolant hoses to help air escape.
- Bleed & Burp the System
- With the cap off, tilt the bike slightly to either side and gently squeeze hoses to release trapped air.
- Start the engine and let it idle for 1-2 minutes. Watch for bubbles rising to the fill neck – top off as needed.
- If your BM50 has a small bleed screw on the cylinder head or radiator, loosen it briefly (with the engine off) until only coolant (no air) comes out, then retighten.
- Repeat adding coolant and burping until the level remains steady and no more air emerges.
- Final Checks
- Reinstall the radiator cap securely.
- Wipe up any spills and check for leaks at all connections.
- After your next ride, allow the bike to cool and recheck the coolant level, topping off if necessary.
Owner's Notes: 1997 Cobra BM50 Tips
- Check coolant frequently. The BM50's small-capacity system means it's unforgiving of leaks or evaporation, especially after a hard moto or in warm climates.
- Never mix coolant types. Always use the same specification fluid to avoid gelling or corrosion in the compact passages.
- Inspect after laydowns. Even a minor tip-over can loosen hoses or burp coolant from the radiator, so always inspect the system if this happens.
- Flush yearly. Replace your coolant at least once per season for best corrosion protection and peak engine cooling.
With these simple steps and expert insights, your 1997 Cobra BM50 will be running at its best every moto. For all your maintenance needs, MotoSport carries the right parts to keep you on the gas.
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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.