Honda TRX400 Maintenance & Repairs

The TRX400 is one of Honda's most popular ATV models, and when powersports pro John Talley does Live Q&A sessions, questions about the maintenance and repairs of this particular model aren't uncommon.

John goes live every Friday at 3pm Eastern, and in this session, he answered quite a few maintenannce and repair questions about the TRX400 Honda ATV. From oil changes to starting and charging problems, here are John's answers to a few of our viewers' questions about the TRX400. 

Honda TRX400 maintenance and repairs

TRX 400 Oil Change

What’s the best oil you would recommend for an older TRX 400EX?

John Talley: The same oil I would recommend for a new 400 EX. That would be the semi-synthetic Honda oil that comes in the gold bottle. You want to make sure it’s the gold, not the gray. The gray has the molybdenum in there and you don’t want that because the clutch would not care for that at all. 

Watch the video above to learn how to change the oil and filter in a Honda TRX400.

Honda HP4 10W-40 engine oil

Honda carburetor cleaner

TRX 400 Starting/Charging Problems

I have a 2008 TRX 400, but I have to jumpstart it every time I ride it. I left it charging but it won’t charge. Any advice?

John Talley: Well, are you sure the battery is in good shape? There are several videos we have out there where I go through the testing procedure to see if it’s your battery, or if it’s your charging system. I’d look at the battery first. What I would need to know is how old it is. Typically if a battery is set up correctly and you have a trickle charger, and you’ve really maintained the health of it, you’re maybe going to get four years tops out of it. And if you didn’t maintain it well, or it wasn’t set up properly initially, I’ve seen them not even last a year, so look at the age of it and go through some of the testing procedures from our videos. 

Watch the video above to learn how to troubleshoot charging problems on a Honda TRX400.

If a Honda 400EX turns over but doesn't crank, would that be the piston losing compression?

John Talley: It could be a combination of several different things. The first thing that you would want to look for is if it’s getting compression, if it’s getting fire, if it’s getting fuel. Put a compression tester on there, and see what it does, see if it’s in range. You should easily be in the 120-140 range on the 400EX, if memory serves. … Do a compression test first, and then work your way from there. I know we did a “Help! My ATV Won’t Start” video, so check that one out and it’ll walk you through some of the electrical things you can look for that would keep it from starting. 

Watch the video above to learn how to troubleshoot starting problems on a Honda TRX400.

TRX 400 Carburetor Problem

How do I fix it when the 400 EX cuts off whenever I come to a stop and takes a while to crank back up, even when it’s in neutral?

John Talley: If it’s cutting off when you’re coming to a stop, that tells me that it’s probably starving for fuel on what I call the idle/air or the pilot jet, the small jet. It shouldn’t do that when you’re coming to a stop … I would say you need to take a peek and make sure it’s getting the fuel that it needs to run, and just idle. And I’m betting we did a video on the carb cleaning on that one.

Watch the video above to learn how to clean the carburetor of a Honda TRX400.

Want to see more live repair questions answered? See more motorcycle and ATV repair questions answered here.  



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