You need to do the infamous Crankase Breather hose re-route. That spray is just the crankcase's unburnt gases being sprayed through the hoses into your airbox. Here's the link to probably one of the most informative posts on this subject: Breather Hose Re-route
It'll seem daunting if you've never took your airbox apart to the point you can access your air filter. Once you get started though, it's easy.
"The tugs on your leash may seem kind or seem cruel;
But the difference is moot to a hard-ridden Buell;
For laws are but chains and it's easy to see;
That only the Outlaw Bueller can ever truly be free!"