Give it a quick clean up with some fine wet and dry paper and see how bad it is. if work is needed find a nice thick flat peice of glass and spread out some fine valve grinding paste then basicly rub the mating surfaces (much like lapping a valve) until your happy. the glass is very important as its completely flat. This method will take the high spots of hard meterial in just a few mins so dont go mad!!! the securing bolts are self tightening 10lbs torque only!!!