I have a Yamaha yfz450. It has aftermarket shocks, steering control thing, tires, foot bars, revbox, recluse clutch kit, yokosomething pipe, kn air filter, coolant heatsink, and a after market **oil tank**

When i first got it none of this was on here and it never leaked oil.
Then recently after i got all this done, it started leaking oil out the back near the swing arm.

I checked the air box and it was full of oil.

I checked the oil level and its fine but still cant solve this problem.

Can somebody help me figure out why the oil is filling the air intake box?

 

Usually when a quad has oil in the airbox it's for one of 2 reasons. Either somebody got a little crazy when they were oiling the air filter and all the excess oil ran into the box, or the oil was overfilled and was forced out through the crankcase breather.

 

Does the crankcase breather come out of the valve cover (at the top of the engine) and go to the airbox? Unhook it and see if its pumping oil out. Next, make sure you're not putting too much oil in it. I know that sounds crazy but if it's like my YZ400F they can be fickle.
Also, it doesn't take much oil to make a mess. One ounce can look enourmous when it spreads out

 

Okay yea i will check thanks for the tips ill give ya all a heads up if its not the problem

 

yea my lil bro did the same thing to his, but what yea is the Yfz?, becasue i think after 04 or 05 they did not utilized the blow out vavle, or crank case breather that is on the head, there are two places where it looks like you put oil, on in the oil pan and one on the side of the case, dont put any in the case, just in the pan, run it for about 10 min then see where the oil is..fill it accordingly, if u put too much oil in it then you may have to tear it down, and see if all is still good..andmake sure you follow what it tells you in the little owner manual they give you and make sure you put the correct amount of mL they tell you. hope this helps