How to Change the Coolant in a 1990 Yamaha XT350
Shop parts for a 1990 Yamaha XT350 Dirt Bike.
Regular coolant changes are critical for keeping your 1990 Yamaha XT350 running cool and protected from internal corrosion. This classic dual-sport features a water-cooled engine – rare for 1990s enduros – making cooling system maintenance especially important.
What You Need
- Socket wrench set (including 10mm socket or wrench)
- Drain pan
- Distilled water
- High-quality motorcycle coolant
- Funnel
- Protective gloves & eye wear
- Shop towels
Step-by-Step Coolant Change Guide
- Let the engine cool completely. Never remove the radiator cap when the engine is hot.
- Remove the seat and side covers to access the radiator cap and coolant hoses.
- Locate the coolant drain bolt. On the XT350, this is a 10mm headed bolt found on the steel pipe running from the cylinder block to the water pump. Have a drain pan ready beneath this area when you remove the bolt. This bolt also has a washer – catch it if it falls.
- Remove the radiator cap to allow coolant to flow out completely.
- Let the old coolant fully drain. Dispose of it safely.
- Flush the system (recommended). Replace the drain bolt and add distilled water to the radiator. Start the bike and run it briefly, then drain the water out. Repeat as needed until the water runs clear.
- Re-install the drain bolt with its washer. Tighten it securely but do not over-torque – the steel pipe is thin and can crush.
- Slowly pour new coolant into the radiator until it reaches the filler neck. Pour slowly to minimize air bubbles.
- Bleed air from the system. Loosen the pump purge bolt gently to vent trapped air; some coolant may escape. Tighten the bolt as soon as only coolant flows out.
- Start the engine with the radiator cap off. Let it idle and occasionally blip the throttle for several minutes to help purge air. Watch for bubbling; add more coolant if needed.
- Once bubbling stops and the level is steady, top up as needed and reinstall the radiator cap.
- Check the coolant reservoir. Refill to the appropriate level if your model is equipped (some XT350s did not include a separate overflow reservoir from the factory).
- Ride and recheck. After your next ride, let the bike cool and double-check both radiator and reservoir levels, topping off if necessary.
XT350-Specific Tips & Notes
- Cooling system capacity is relatively small compared to modern bikes. Don't overfill.
- Be gentle with aging plastics and rubber hoses. If your radiator cap, hoses, or gaskets look cracked or swollen, now is the time to replace them.
- Inspect the water pump area for leaks, especially at the drain bolt washer and pipe joints.
- The XT350 uses a compact water pump bolted to the engine case. Overtightening bolts or using poor-quality coolant may cause early failures.
- Never use tap water – stick to distilled water and motorcycle-specific coolant to prevent lime-scale buildup and internal corrosion.
By following this procedure, you'll keep your 1990 Yamaha XT350 cool and ready for the next adventure, on or off road. All maintenance should be done with care and safety in mind. When in doubt, consult your service manual or trusted mechanic.
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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.