The crankcase breather ,for emission purposes, runs from the motor to the air box so the blow by is burned in the motor. Many bikes have what is called a pollution tube that runs from the box to just in front of the rear wheel.This is to drain the **** that does not get sucked into the motor (oil,water,etc) Place a pie tin or pan on the ground and pull the plug out of the tube and all the horrible gack from the air box will drain into the pan. This is periodic maintenance that never seems to get mentioned anywhere. Now you know.