Honda GX390: Oil Change and Other Maintenance On Your Own

For the Honda GX390 to keep performing in its peak condition, it has to have regular oil changes and other maintenance protocols. This article will cover how to change the Honda GX390 engine oil and perform other maintenance procedures on your own to keep your engine in good condition. Let's start with what Honda GX390 is.

What is Honda GX390?

Honda GX390 is a commercial-grade engine commonly found in machines such as agricultural equipment, pressure washers, generators, construction equipment, pumps, welders, garden equipment, commercial lawn, small vehicles, and other industrial machines.

The engine features a maximum power output of 13 horsepower at 3600 rpm. It's an upgrade of its predecessors because it has lower emissions and is more fuel efficient. The horizontal crankshaft engine from Honda comes with a 3-year limited residential warranty along with a 3-year commercial warranty.

Some of its specs include:

• A fuel tank with a capacity of 6.2 liters.
• A 4-stroke single-cylinder gasoline engine type that weighs approximately 78 pounds or 36 kg.
• A compression ratio of 8.2: 1.
• A recoil starting system with a separate electric starter kit that serves as a backup.
• A variable ignition timing.
• A cast iron sleeve cylinder that enhances heat loss to facilitate cooling of the engine.
• A forced lubrication system that has a spin-on oil filter.
• Maximum Net torque of 26.5 Nm or 2.7 kgfm.

Now that you know the Honda GX 360 and its specs, let's look at why you need to do an oil change.

Why Do You Need to Change the Oil of the Honda GX 390?

Before changing the oil of the Honda GX 390 engine, it's always best to confirm your engine oil capacity and oil type. You can get this information from the engine owner's manual. The engine oil capacity of the Honda GX 390 is 1.1 liters or 1.16 quarts.

You should use high-quality synthetic oil or SAE 10W-30-1 general-use oil for four strokes automotive engine. The 10 W in SAE 10W-30-1 represents the oil's viscosity meaning 10-weight oil at 0 degrees Fahrenheit, while the 30 illustrates 30-weight oil when the engine heats up to 210 degrees Fahrenheit.

This means that the engine oil has the ability to change viscosity depending on the engine's temperature, which enables the engine to operate safely, reducing its wear and tear. Using the correct recommended oil ensures the engine runs smoothly and prevents a void of warranty. 

Like a car's engine oil, the Honda's GX 390 engine oil needs regular changes. This is due to dirt build-up and oil breakdown due to moving parts that reduce the oil's ability to absorb heat and lubricate the engine.

Honda's recommended time frame for an oil change is every 100 hours or six months for conventional oil. Synthetic oil is more durable than conventional oil and therefore has a longer time frame for the oil change.

Signs you can use to determine that the engine oil needs change are:

• The oil has a coarse feel to it.
• The oil has a black or dark brown color as opposed to amber or light brown color when clean.
• Unusual sounds or smells, such as smoke coming from the engine.
• A decline in the engine's performance.

How to Change the Honda GX 390 Engine Oil

Regular oil change extends the engine's lifespan and helps it run smoothly. Some materials you'll need for an engine oil change are a drain pan, a wrench, a funnel, and the new recommended engine oil. Below are the steps to take to change the engine oil. 

• Before you start with the oil change, run the engine until it reaches its normal temperature to warm up the oil and ensure it drains easily.
• Put the drain pan under the engine to collect the old engine oil.
• Unfasten the old drain plug and seal the washer. The drain plug is a small screw or bolt at the bottom of your engine.
• Let the old oil completely drain into the drain pan and appropriately dispose of it or take it to auto repair shops that recycle used oil.
• Reinstall the drain plug and tighten it securely.
• Remove the old fill cap you can find at the top of the engine.
• Refill the engine with the new recommended oil with the help of a funnel inserted into the oil filler hole.
• Use a dipstick to check whether the oil has reached the recommended level, and if not, add until it reaches that level.
• Restore the fill cap and use a rag to wipe off the oil spills.
• Turn on the engine and leave it to run for a few minutes to allow the new oil to circulate. Top up the oil if necessary.
• You should also replace the oil filter to enable the engine to function properly. The oil filter's location depends on which type of equipment the Honda GX 390 engine serves.

How to Maintain the GX 390 Engine

To increase its lifespan and allow a safe and economical operation, you have to maintain the engine by regularly servicing it. To properly maintain the engine, you need to follow the right maintenance procedures with the necessary tools, perform routine inspection procedures, and have a maintenance schedule.

Failure to properly maintain the engine can make the engine prone to malfunctions which can lead to serious injury or even death. Repair or replacement of engine parts needs to be done using genuine engine parts that are EPA-certified standards. Before you embark on engine maintenance, there are some safety procedures you need to follow. 

Safety Procedures to Follow Before Engine Maintenance

Below are some safety protocols to follow before you begin the engine maintenance. 

• Switch off the engine before starting a do-it-yourself (DIY) maintenance procedure. This is to prevent any accidents such as burns due to hot engine parts, cuts and bruises due to moving engine parts, or carbon monoxide poisoning due to the gases the engine emits.
• Keep sparks, cigarettes, and flames away from the engine to reduce the chances of an explosion or fire.
• Ensure you have the right tools and skills to handle the maintenance procedure you are about to conduct. If you need help, let your service dealer handle the procedure.
• Go through the instructions in the maintenance manual.

Ways to Service the Honda GX 390 Engine

Apart from oil change, there are other maintenance procedures to service your engine. Here are the main ones.

1) Air Filter Check

The air filter ensures only clean air enters the engine by preventing harmful contaminants from entering the engine. Here's how to conduct an air filter check. 

• The first step is to remove the air cleaner cover to expose the air filter elements.
• Disconnect the air filter by removing the air filter wing nut.
• Separate the air filter components- the foam filter from the paper filter.
• Check for any signs of damage or corrosion on the foam filter or paper filter. Replace either or all the filters if damaged.
• If the filters aren't damaged, clean them for reuse. To clean the paper air filter, tap it on a hard surface or use compressed air for dirt removal. Avoid brushing off the brush since it'll enter the fibers. To clean a foam air filter, wash it with warm soapy water or nonflammable solvent, rinse it, let it dry, and dip it in clean engine oil. You can also use a wet rag to clean the inside of the air cleaner cover and base.
• Reassemble the air filter components and securely reinstall the air filter wing nut.

2) Spark Plug Inspection

To avoid engine misfiring and start-up trouble, you need to properly inspect the spark plug to ensure it's in good condition. Here's how to inspect it.

• Remove the spark plug cap.
• Use a spark plug wrench to unscrew the spark plug.
• Check the spark plug for any signs of a chipped or cracked insulator or a worn-out electrode. Replace the spark plug if you find any of those symptoms.
• If the spark plug is in good condition, use a wire brush to remove dirt.
• Carefully reinstall the spark plug by hand to prevent cross-threading.
• Tighten the spark plug with a wrench to compress the washer.
• Return the spark plug cap.

3) Engine Oil Level Inspection

Before inspecting the oil level, ensure the engine is on level ground. Here's how to check the oil level. 

• Push out the dipstick and wipe it clean with a clean rag.
• Return the dipstick to its place and remove it again to observe the oil level on the dipstick.
• If the oil level is below the recommended level, top up the oil to the required point.

4) Adjusting the Idle Speed

• Switch on the engine and let it run until it warms up to the normal operating temperature.
• Turn the throttle lever until it reaches its slowest position.
• Use a screwdriver to turn the throttle stop screw until it reaches the standard idle speed of around 1400 rpm.

Bottom Line

There you have it-how to change the oil and maintain the Honda GX390 on your own. If you don't have the necessary skills and tools for maintenance, it's best to leave it to trusted service dealers who can safely service the engine.