How to Change the Coolant in a 1990 Suzuki DR350: A MotoSport Guide
Shop parts for a 1990 Suzuki DR350 Dirt Bike.
Regularly changing the coolant in your 1990 Suzuki DR350 is one of the simplest – and most crucial – maintenance steps to keep your dirt bike running cool and efficiently. This guide from MotoSport walks you through a robust, step-by-step process specifically tailored for the DR350, and highlights unique points to consider for this classic model.
What Makes the 1990 DR350 Unique?
The 1990 DR350 is air & oil-cooled with an auxiliary oil cooler rather than a traditional full liquid-cooling setup. However, if your DR350 has an aftermarket or custom liquid-cooling system, or you are dealing with the coolant for the auxiliary oil cooler, follow these steps for best results. For factory-correct models, ensure you are actually servicing coolant if modifications have been made, as the stock DR350 does not feature a conventional radiator setup found on many modern machines.
What You'll Need
- Appropriate coolant (check for compatibility if using a custom setup, but typically use motorcycle-specific coolant)
- Distilled water (for system flushes; never use tap water)
- Drip pan or container (for catching old coolant)
- Socket and wrench set (likely 8mm or 10mm for most drain bolts)
- Funnel
- Protective gear (gloves, safety glasses)
- Shop towels/rags
Step-by-Step Coolant Change Procedure
- Let the Engine Cool
Always start with a cool engine to avoid burns as the cooling system can be under pressure. - Remove the Skid Plate (if installed)
Unbolt the skid plate to access the underside of the engine and water pump area if your bike has an aftermarket liquid-cooling modification or a sump-style plug. - Locate the Drain Bolt
For a DR350 with liquid cooling, look for the drain bolt at the bottom of the water pump cover. Place your drip pan directly under this bolt.
If draining the auxiliary oil cooler, follow the hose routing and any drain provisions installed by the aftermarket system. - Drain the Old Coolant
Loosen and remove the drain bolt. For faster flow, remove the radiator or filler cap. Allow all coolant to drain completely.
Properly dispose of used coolant – never pour it down the drain or onto the ground. - Flush the System (Recommended)
Pour distilled water into the radiator/filler neck and allow it to flush through. Replace the drain bolt/nut and refill a second time if the fluid coming out remains discolored or contaminated. Repeat until the water runs clear.
Optional: A 50-50 mix of distilled water and vinegar can help break down stubborn deposits if the system is especially dirty. Follow with one more flush using pure distilled water. - Replace the Drain Bolt
Reinstall and securely tighten the drain bolt. Use a new washer if necessary to prevent leaks. - Fill with Fresh Coolant
Slowly pour the new coolant into the radiator or filler neck. Tilt the bike gently from side to side and gently squeeze hoses to help remove air pockets. Fill until you reach the correct level at the neck or as specified for your DR350's custom system. - Bleed Air From the System
Leave the radiator cap off. Start the bike and let it idle briefly. Watch for bubbles escaping – this indicates trapped air is bleeding out. Once the bubbles stop, top off coolant as needed. Shut off the engine and install the cap. - Check for Leaks & Coolant Level
After running the bike to full operating temperature and cooling completely, recheck the coolant level. Add if necessary, and inspect for any leaks at hose connections or the drain bolt.
Extra Tips for the 1990 DR350 Owner
- If your DR350 is not fitted with an aftermarket cooling system, standard coolant service is not required – focus on maintaining your oil cooler system instead.
- Vintage plastics and seals on older DR350s can become brittle with age; inspect all components for cracks or leaks before reassembly.
- Never use tap water for flushing; mineral deposits can accumulate and compromise cooling performance or create clogs.
- Always use a motorcycle-specific coolant free of silicates and phosphates, unless your system calls for something different.
Final Check & Next Steps
Go for a short test ride, watching engine temperature and checking for leaks once the bike has cooled. Repeat the coolant level check after your next ride to ensure it's holding steady.
Keeping your 1990 Suzuki DR350 running strong takes just a few simple steps. For any parts, gaskets, or new coolant, MotoSport has you covered for everything you need to keep your ride in top shape.
Related Shopping Categories
Shop Radiators for a 1990 Suzuki DR350 Dirt Bike.
Shop Coolant for a 1990 Suzuki DR350 Dirt Bike.
Shop Temperature Sensors for a 1990 Suzuki DR350 Dirt Bike.
Shop Tools for a 1990 Suzuki DR350 Dirt Bike.
Shop Radiator Hoses for a 1990 Suzuki DR350 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.