How to Change the Oil on a Honda Rancher 420

An oil change on your Honda Rancher is standard maintenance, and an important way to keep your ATV's engine healthy. 

How often should you change the oil on your Rancher 420? Honda recommends every 12 months, 100 hours, or 600 miles: whichever comes first. Here's how to do an oil change on a Honda TRX 420.

Tools and Parts Needed - Honda Rancher TRX420 Oil Change

Tools

  • 3/8th ratchet
  • 17mm socket
  • 8mm socket
  • Torque wrench

PRO TIP: There are two different Honda motor oils you can use for this job. GN4 is a standard oil, but if your engine works a little harder, we recommend using Honda HP4 semi-synthetic oil instead. 

Changing the Oil on a Honda Rancher

Step 1. Run the engine for a couple of minutes to circulate the oil. 

PRO TIP: You don't need to bring the engine all the way up to temperature, but circulating the oil a little will make it easier to drain. 

Step 2. Remove the plastic panels on both sides of the unit. You can pull them out by hand without any tools.  

Honda Rancher 420 oil change prep

PRO TIP: Removing the right side panel allows you to access the oil filter, and on the left hand side you'll find the oil fill cap. Removing it makes it easier for the oil to drain out.

Honda Rancher ATV oil change

Step 3. Find the drain bolt underneath the unit to remove the used oil, and get a drain pan to catch the oil. See #7 in the Rancher crankcase diagram to find the bolt's location. Access the drain bolt through the hole in the skid plate, and use your 17mm socket to remove it. 

NOTE: Be careful not to lose the crush washer on the bolt. If you need to replace it, Honda has a drain bolt crush washer available for purchase. 

Honda Rancher 420 TRX oil change

Step 4. Remove the old oil filter while the used oil drains. The filter is found on the right side of the engine and can be seen as #4 in our Rancher front crankcase cover diagram. Some oil will leak out, so get a rag underneath it to avoid a mess. Take off the three 8mm bolts to remove the cover and expose the filter, then pull the filter out. 

Honda Rancher 420 oil filter change

Honda Rancher ATV oil filter change

NOTE: There's a spring behind the filter that should remain in place. 

Honda Rancher TRX420 oil filter change

Step 5. Replace the oil filter. One side of the filter will have "Outside" stamped in the metal. It's crucial that this side faces out toward you when you install the filter. Make sure the spring is behind the filter and then slide it in place. 

Honda Rancher 420 oil filter replacement

Step 6. Inspect the O-rings on the oil filter cover and around one of the bolt holes for the cover. Make sure they are not cut or damaged. Then, replace the filter cover and the three 8mm bolts without over-tightening them.  

Honda Rancher 420 oil filter O-rings

Honda TRX 420 Rancher oil filter cover

Step 7. Replace the right-hand side plastic. There's a tab at the bottom of the plastic piece. Hook it into place first, then push the rest of the plastic into place and snap it.  

Oil change Honda Rancher TRX

Honda Rancher 420 change oil

Step 8. Replace the drain plug. Hand-tighten it first to get it threaded, then use a torque wrench to tighten it to 18 foot-pounds.   

Honda Rancher 420 oil drain plug replacement

Step 9. Refill the engine with oil. 

PRO TIP: Honda says the oil capacity of the Rancher 420 is 3 quarts, but we found that can be a little too much. Pour in 2.5 quarts, replace the fill cap, run the engine for a couple of minutes, and then check the level. To check the oil level on the engine, don't screw in the fill cap. Just plunge it in and remove it, then top the engine off with oil to set the level. 

Honda Rancher ATV oil change refill

Honda TRX420 oil change dipstick

Step 10. Replace the fill cap.  

Step 11. Replace the plastic cover and you're done.  

Honda Rancher plastic covers

Now that you've got the engine oil change done on your Honda TRX 420, why not go ahead and change rear differential oil while you're at it? Watch the video below to see how to change the drive shaft oil on a Honda Rancher 420

 

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