Answer by  
                                                                                          musicman (31)
                                                            
                          
                          
                                                           Assuming that the horn is being used, take off the bottom valve cover and loosen the top valve cap. Using the "butt" end of a wooden serving spoon or a 2B drumstick, tap the valve gently but firming and be careful. Then clean valve and valve casing; oil and return valve.