ON CERTAIN MOTORCYCLES, THE CRANKCASE BREATHER SEPARATOR MAY BE DEFECTED. DURING THE MOLDING PROCESS, THE BREATHER PASSAGE MAY HAVE BEEN BLOCKED BY A THIN LAYER OF THE INJECTED PLASTIC MATERIAL. THIS BLOCKAGE WILL CREATE A BUILD-UP OF PRESSURE INSIDE THE CRANKCASE AND MAY CAUSE THE LEFT SIDE ENGINE SEAL TO BE PUSHED OUT OF POSITION AND AN OIL LEAK WILL OCCUR.