2009 Polaris Sportsman 850 XP EFI EPS Service Manual, Page 125Get this manual
ENGINE NOTE: When using an interference angle, the seat contact point on the valve will be very narrow, and is normal conditionLook for an even and continuous contact point all the way around the valve face (A)89Clean all filings from the area with hot soapy waterRinse and dry with compressed airLubricate the valve guides with clean engine oil, and apply oil or water based lapping compound to the face of the valve
NOTE: Lapping not required if an interference angle reconditioning method is used
10Insert the valve into its respective guide and lap using lapping tool or section of fuel line connected to the valve stem11Rotate the valve rapidly back and forth until the cut sounds smoothLift the valve slightly off of the seat, rotate 14 turn, and repeat the lapping processDo this four to five times until the valve is fully seated, and repeat process for the other valve(s)12Thoroughly clean cylinder head and valves