2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 83Get this manual
ENGINE 16Remove valve and check where the Prussian BlueTM indicates seat contact on the valve faceThe valve seat should contact the middle of the valve face or slightly above, and must be the proper width If the indicated seat contact is at the top edge of the valve face and contacts the margin area it is too high on the valve faceUse the 30o cutter to lower the valve seat If too low use the 60o or 75o cutter to raise the seatWhen contact area is centered on the valve face, measure seat width If the seat is too wide or uneven, use both top and bottom cutters to narrow the seat If the seat is too narrow, widen using the 45o cutter and re-check contact point on the valve face and seat width after each cutValve Seat Width: Intake Std: .028" (.7 mm) Limit: .055" (1.4 mm) Exhaust Std: .039"(1.0 mm) Limit: .071" (1.8 mm) 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 on the black marked area, all the way around the valve face17Clean all filings from the area with hot soapy water, rinse, and dry with compressed air18Lubricate the valve guides with clean engine oil, and apply oil or water based lapping compound to the face of the valveLapping is not required with an interference angle19Insert the valve into its respective guide and lap using lapping tool or section of fuel line connected to the valve stem20Rotate 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)21Clean cylinder head, valves, and camshaft oil supply passage (A) thoroughlyA