I have recently purchased a low hour 1 owner 2007 TRX450ER. So far I like it a lot. After my first long trail ride I noticed some oil in the intake boot as well as on the filter. Upon closer inspection I determined the oil is motor oil and not air filter oil. I did see some evidence that this was coming in from the CCV. This quad seems to have plenty of power and I have not noticed any smoke from the exhaust so I do not think this is coming from worn piston rings. It starts and runs perfectly. According to the seller it still has the original chain and sprockets as well as brake pads so I tend to believe that the hours are indeed low. Very little boot wear on the frame or on the engine covers. So what issues could cause this oil in the air box? I did changed the oil before riding it and refilled with the exact amount specified by the manual (690mL).
Footy
Today I checked both engine vents and the transmission vent hose for blockages. All 3 of these are flowing freely. I also checked the hose running from the "T" to the airbox. It is clear as well. I believe the oil is traveling up the lower engine vent hose (CCV) and from there to the airbox, I was wondering if standing the quad up on the grab bar would cause oil to travel through the lower vent hose and into the airbox. I had the quad standing up while washing it.
Are you running the same oils for the trans and engine? A lot of us run Rotella in both sides of the case. If so this might not help. If there is the red Honda trans fluid it, then you should be able to tell if its motor oil or not. 99% of the time its the transmission breather hose attached at the wrong location. Pretty easy to get confused by this, as the breather hose fits like a glove on the carburetor nipple/stem. However this blocks the breather off, causing pressure on the transmission, and she'll spit oil inside the airbox. I attached a picture showing the proper location for this hose. This might not be the problem, but its quick to fix, if it is, happens a lot, easy to do. Let us know what you find.
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