How to Change the Oil in a Honda TRX 400 ATV 

Regular oil changes for your Honda ATV can slow the toll that heat and pressure take on its engine, helping it to run smoothly season after season. 

Doing your own Honda ATV oil change is a quick and inexpensive process that even novice mechanics can perform as part of a regular ATV maintenance schedule. Watch the video above and follow the steps below to change the oil and oil filter in a Honda TRX 400.

Tools and Parts Needed - Honda TRX 400 Oil Change


NOTE: A Honda ATV works on a dry sump system, meaning it has oil in both the crankcase and the oil tank. You will need to drain both.

Honda TRX 400 oil change crankcase

Honda TRX 400 EX oil change tank

Honda TRX 400 ATV Oil Service Steps

Step 1. Run the engine for a couple of minutes to get the oil circulated through the system. Stop the engine, then loosen the dipstick (located on the left side of the motor) and place a drain pan underneath the motor. 

Honda TRX400 ATV oil change service

Step 2. Use a 12mm socket to remove the drain bolt for the crankcase (located low around the circular crankcase cover) and the crush washer behind the drain bolt, making sure not to lose the washer as the oil comes out. 

Honda TRX400 oil service

Step 3. Place the drain pan underneath the oil tank and use your 14mm socket to remove the oil tank drain bolt (located in front of the engine), again making sure not to lose the crush washer behind it when you pull the bolt out.

Honda TRX 400EX oil change

NOTE: While the crankcase and oil tank drain, move over to the right side of the engine to change the ATV’s oil filter.

Step 4. Use your 8mm socket to loosen the two bolts holding the oil filter cover in place.

Honda TRX400 ATV oil filter

NOTE: The oil filter cover is a small cylinder next to the larger circular crankcase. Place something underneath the cover to catch oil that spills from removing it. 

Step 5. Remove the oil filter, making sure to keep the spring behind it hanging on the case inside the filter chamber. 

Honda TRX400 EX oil filter

NOTE: Don’t lose the spring, since it needs to stay in place behind the new filter.

Step 6. Install the new oil filter with the word “outside” stamped on the filter facing the outside of the engine (facing toward you). 

Honda TRX400 ATV oil filter installation

NOTE: Make sure the spring is still hanging at the back of the chamber before you install the new filter. Putting the filter in backward causes serious engine damage.

Step 7. Replace the filter cover and its two bolts, then tighten the bolts snug.

Honda TRX 400EX oil filter cover

Step 8. Tighten the 14mm drain bolt with the crush washer on the oil tank, then do the same with the 12mm bolt on the crankcase. Thread both by hand first, then tighten them to 12 or 13 foot-pounds of torque. 

Honda TRX400 oil change service

Step 9. Fill the engine with 1 quart of Honda 10W40 motor oil. Next, screw the dipstick in place and run the motor for 10-15 seconds to circulate the oil. Stop the engine, then add another ¾ of a quart and replace the dipstick, and run the engine again for about two minutes. Finally, top off the oil to bring the level on the dipstick to about three-quarters capacity.

Honda TRX400 engine oil change

NOTE: The Honda TRX 400 uses 1.9 quarts of oil. Before filling it up, check the capacity of your engine, and keep in mind that all of the oil will probably not go in at once. Some oil has to move up into the crankcase to make room for more in the oil tank.

Honda ATV oil change service dipstick

That’s all it takes to perform your own Honda ATV oil change, but your work is not quite finished. Complete the job by taking your used oil to a recycler for proper disposal. 


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