Honda TRX350 - TRX400 ATV Repair Q&A

There's never a shortage of Honda ATV repair questions during powersports pro John Talley's weekly live Q&A sessions, especially for the popular Rancher TRX350 and TRX400 models.

John Talley goes live every Friday at 3pm Eastern on our YouTube channel, and in this edition he addressed several Honda ATV repair issues, including smoking TRX350 and TRX400 engines after top end repairs.

Honfa TRX350 Rancher ATV repair

Honda Rancher TRX 350

I have a 2006 Honda Rancher 350 and I just put a new top end in it because it was smoking pretty bad. About a week later, it started smoking again. What’s wrong with it? 

John Talley: When you said you did the top end, did you just do the piston and rings, and did you take a look at your valves to see if there was any slop in the valve guides? Did you check your valve seals? … We did a video on how to break in a top end or an engine rebuild. … the first cycle, you just want to heat cycle it without running it too hard. After that, I would go ahead and hammer it. That way those rings get heated up, and you get a lot of compression built up and they start expanding out, cutting into the walls and the walls cutting into them … Also, if you did do just pistons and rings, are you sure that you went in and gapped your rings appropriately? Because if you didn’t, then the rings don’t have enough room to expand and contract and they actually push into each other, and that causes them to wear prematurely. 

Watch the video above to see how to tear down the top end of a Honda TRX 350 ATV.

I go trail and mud riding on my 06 Rancher 350, so what should I check for when I get back each time? 

John Talley: Well, first and foremost the air filter. That is the #1 thing to look at. … Sometimes I’ll do an oil change after every single weekend because we run our machines pretty hard. Oil is also a lot cheaper than rebuilding an engine, so why not keep it as fresh as you can? On the 350, especially if you’re in the mud a lot, you need to keep an eye on your rear brake, that housing going around your brakes. Over time that O-ring will break down … as well as that seal which your axle goes through … and if water gets in there, it makes a mess out of your brakes.

Watch the videos above to see how to change the oil and the air filter of a Honda TRX350 ATV.

Buy Honda GN4 10W-30 oil

Buy Honda Rancher 350 air filter

Honda TRX400/TRX350

My 400EX is smoking pretty bad and my top end was done not too long ago. Any thoughts?

John Talley: I would give you the same advice I gave a previous person about their 350. Are you sure that you gapped your rings correctly, and did you break them in? The way I break them in is, I run it kind of soft for the first heat cycle, which is usually 5-10 minutes. After that, I put the coals to it for about 30-45 minutes, maybe an hour, and then let it cool down and at that point, they should be seated in. If you did that and it’s still smoking, I would be suspect of the valve guides or more than likely, the valve seals. 

Watch the video above to see how to do a top end rebuild on a Honda TRX 350 ATV.

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







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