How to Change the Coolant in a 1987 Yamaha YZ250: Keep Your Classic Motocrosser Cool
Shop parts for a 1987 Yamaha YZ250 Dirt Bike.
Properly maintaining the cooling system on your 1987 Yamaha YZ250 helps ensure maximum performance and engine longevity. This legendary two-stroke has an open and simple cooling system, but its vintage construction means regular service is essentialespecially with older aluminum radiators and heads that can be susceptible to corrosion.
Below is an exclusive MotoSport guide tailored for the 1987 YZ250, covering all the key steps and tips you need to change the coolant like a pro.
What You Need
- New coolant (high-quality ethylene glycol anti-freeze with anti-corrosion additives for aluminum engines)
- Distilled or soft water (for mixing if using concentrate)
- Drain pan
- 8mm or 10mm socket or wrench
- Funnel
- Clean rag
- Torque wrench (recommended) for reinstalling the drain bolt
Coolant Type & Capacity for Your 1987 YZ250
- Install as a 50% coolant / 50% distilled or soft water mix for best protection
- Total cooling system capacity is 1.2 liters (about 1.27 US quarts)
Step-By-Step Coolant Change Instructions
- Prep the bike: Make sure the engine is completely cool to prevent burns. Stand the bike on a level surface using a stand.
- Access the radiator cap: Remove the side shrouds or panels as required to reach the radiator. Open the radiator cap slowly to relieve any pressure.
- Drain the coolant: Place your drain pan under the engine. Locate the coolant drain bolttypically on the lower right side of the cylinder or the engine case near the water pump. Loosen and remove the bolt along with any copper washer. Allow the coolant to drain fully.
Extra MotoSport tip: Loosen the bleed screw (if present) on the cylinder head to improve drainage and reduce air pockets. - Flush the system: Reinstall the drain bolt (finger-tight) and fill the system with clean tap water. Replace the radiator cap and start the engine. Run the bike for a minute at idle to circulate the water, then shut it off. Allow to cool, repeat the drain process, and repeat until the drained water is clear.
This step is critical for vintage bikes that may have residue or corrosion inside the system. - Install the drain bolt: Inspect the copper washer and replace if damaged. Tighten the drain bolt to 10 Nm (– 7.2 ft–lb) to prevent leaks.
- Add new coolant: Mix coolant and distilled water in a 1:1 ratio if not pre-mixed. Fill the radiator slowly to the base of the filler neck. Squeeze the radiator hoses gently to help remove trapped air as you fill.
- Bleed the system: If your model has a bleed screw on the cylinder/head, open it until coolant flows out without bubbles, then retighten. Otherwise, lean the bike side to side and tap the hoses to release air pockets.
- Warm-cycle and top off: Replace the radiator cap and start the engine, letting it run until it reaches normal operating temperature. Shut it off and let it cool to ambient temperature. Recheck the coolant level and top off if needed—some drop is normal as air escapes and fluid replaces it.
Model-Specific 1987 YZ250 Notes
- The 1987 YZ250's radiators and cylinder head are made from aluminum. Always use coolant with anti-corrosion protection for aluminum-compatible systems.
- Vintage plastic radiator tanks can become brittle—avoid overtightening bolts and inspect for leaks each season.
- This model does not have a coolant expansion reservoir. Monitor coolant levels regularly and look out for unexplained drops, which may indicate leaks or head gasket issues.
- The system is simple and robust, but debris in older bikes can clog passages. Occasional flushing is especially important on classic MX machines.
When to Change Your Coolant
- Change at least once a year or every 25–30 hours of riding, whichever comes first.
- Replace anytime you see rust, discoloration, or sediment in the coolant.
Extra Pro Tips
- Check the radiator cap for a secure fit and healthy gasket. Weak caps allow the system to boil over prematurely.
- On old bikes, inspect water pump seals for weeping. If leaking, replace before adding new coolant to avoid contamination and costly repairs.
Keeping your 1987 Yamaha YZ250's cooling system fresh is easy and pays off with improved reliability and performance on the track or trail. If you need OEM or performance replacement parts for maintenance, Shop parts for a 1987 Yamaha YZ250 Dirt Bike.
Related Shopping Categories
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Shop Radiator Hoses for a 1987 Yamaha YZ250 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.