Why Is There Oil in My Honda ATV's Airbox?

What does it mean when you find oil in the airbox of a Honda ATV? Maybe it's low compression, spent combustion or both, that could be causing blow-by from the crankcase. 

Partzilla's resident Honda ATV expert John Talley does live Q&A sessions every Friday at 3pm Eastern on our YouTube channel. In this edition, John was asked what could be the reason a Rancher TRX350 has oil in the airbox. 

Honda ATV oil in airbox

Honda Rancher 350 Oil in Airbox

I have a 2001 Honda Rancher 350. Why would my airbox have oil sitting on the bottom it? 

John Talley: Mainly because there is a crankcase on almost all engines and yours may be starting to get a little lower on compression, and it’s getting a lot of blow-by. And when that goes down into the crankcase, it builds up pressure, and of course it relieves that pressure and with a rubber line that goes up to the air box. Well, along with that spent combustion, if you will, that goes down into the crankcase, it also may pick up a little bit of oil on the way in a mist form and just spit it into the airbox. So that’s more than likely where it’s coming from. Or if you rolled it over by chance, of course that rubber line is going to take a big gulp of that air and oil and then dump it into the airbox if you flipped it on its wheels. But yeah, that’s where it’s coming from, your engine cases.

Watch the video above to see how to change the oil in a Honda Rancher 350 ATV.

Buy Honda ATV oil filter

Buy Honda ATV air filter

Watch the video below to see how to change the air filter in a Honda Rancher 350 ATV.

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

 
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AIR FILTER
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