2010 Polaris Sportsman 850 Service Manual, Page 130Get this manual
ENGINE Valve Seat Reconditioning
Valve seat reconditioning should be performed by technician proficient in cylinder head reconditioning techniquesReconditioning techniques vary, so follow the instructions provided by the valve reconditioning equipment manufacturerDo not grind seats more than necessary to provide proper seat surface, width, and contact point on valve face If the contact area of the initial cut is greater than 75, continue to cut the seat until all pits are removed and new seat surface is evidentNOTE: Remove only the amount of material necessary to repair the seat surface5To check the contact area of the seat on the valve face, apply thin coating of Prussian Blue paste to the valve seatIf using an interference angle (46apply black permanent marker to the entire valve face (A)
Valve Seat Inspection