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?

 

What does "full" mean??? Is it all wet, or are we talking an inch of oil in the bottom???

Might be that you are passing compression past the rings for example, and it has nowhere to go but out the vent and it takes oil with it.

 

idk it possible
all i know is that when it runs and just sits there
oil drops from the air intake box from the bottom where the plug is

 

If it's just a little oil in the bottom of the airbox, that's nothing to worry about. If the oil level in the crankcase isn't going down, might be that the oil is draining off the air filter.

Also, do you ever stand the bike up on the rear bar? If you do that and forget to turn the fuel valve off, it can sometime leak gas back throught he air filter and leach the oil out of it.