How to Change the Coolant in a 1987 Yamaha YZ490
Shop parts for a 1987 Yamaha YZ490 Dirt Bike.
Keeping the cooling system in peak condition is crucial for the legendary air-cooled – and, in some late models, liquid-cooled – performance of the 1987 Yamaha YZ490. Though renowned for its raw power and potent two-stroke delivery, proper coolant maintenance ensures the engine's longevity, optimal output, and consistent riding experience. This exclusive MotoSport.com guide details everything you need to know for a professional-grade coolant change on your YZ490.
Why Coolant Changes Matter for the YZ490
The YZ490's high-displacement two-stroke engine generates significant heat. Old, degraded coolant can lead to overheating, increased wear, and in serious cases, engine failure. The 1987 model's cooling system relies on clean, functional coolant to dissipate heat efficiently, so regular coolant service is paramount.
What You'll Need
- Fresh, recommended motorcycle coolant (silicate-free, pre-mixed or concentrated as required)
- Drain pan or suitable container
- Rags and water for cleanup
- Socket set and screwdrivers
- Replacement sealing washer (recommended)
- Protective gloves & eye protection
Coolant Change Instructions
- Allow the bike to cool completely. Never open the radiator cap on a hot engine – hot coolant is pressurized and can cause serious burns.
- Remove the radiator cap to relieve any residual pressure.
- Place the drain pan under the engine area below the water pump or drain bolt.
- Locate the coolant drain bolt (typically on the lower water pump cover) and remove it, along with the sealing washer. Allow all old coolant to drain completely.
- Inspect and replace the sealing washer on the drain bolt if worn or damaged before reinstalling it. Tighten gently to manufacturer torque specs.
- Flush the system (optional, but recommended for older machines):
- Fill the radiator with distilled water.
- Replace the radiator cap and start the engine briefly to circulate water.
- Turn off the engine, allow it to cool, and repeat the draining process until the drained water appears clean.
- Refill with fresh coolant up to the base of the radiator filler neck. Be sure to use the correct coolant type for motorcycles.
- Reinstall the radiator cap securely.
- Start the engine and let it warm up. Allow the bike to go through a heat cycle so the thermostat opens, and any trapped air works its way out. Watch the coolant level as the bike runs; the coolant will expand and contract, helping release air pockets.
- Cool down the bike completely and recheck the coolant level in the radiator and reservoir. Top off with more coolant as needed.
Tips & Things to Watch For
- Coolant Leaks: Inspect around the drain bolt, hose connections, and radiator for leaks after service. Replace any worn hoses or clamps.
- Air Pockets: Trapped air can cause overheating. Always cycle the engine and top off coolant as the system stabilizes. If you notice repeated drops in coolant level, check for ongoing leaks or air pockets.
- Corrosion: Using the proper coolant (and not just water) prevents corrosion inside the mixed metal radiator and engine. Never run the YZ490 on pure water for extended periods.
- Service Intervals: Check and replace coolant at least once per year, or more frequently for heavy riders and racers.
Special Notes for 1987 YZ490 Owners
- This model YZ490, a powerhouse in vintage motocross, is famed for rugged simplicity and easily serviceable components. However, it remains sensitive to overheating due to its high-performance two-stroke design – overlooking coolant maintenance can cause seized pistons or cylinder warping.
- If restoring or upgrading, inspect the radiator closely for internal corrosion and consider flushing the system with a 50/50 vinegar-water mix if buildup is severe. Follow by several distilled water flushes to remove all acidity.
- Always use coolants formulated for motorcycle aluminum radiators. Avoid automotive coolants containing silicates or phosphates that can damage internal passages.
Stay ahead of maintenance and keep your iconic YZ490 pulling hard for years to come. For all your vintage Yamaha and performance dirt bike needs, choose MotoSport.com – your source for expert parts, service, and riding gear.
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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.