2008 Polaris ATV Predator 50, Sportsman Outlaw 90 Service Manual, Page 61Get this manual
ENGINETRANSMISSION 5Install the valve in its mating guide and lift it 5mm off of the seatPush valve back and forth and measure deflection in two directionsIf deflection exceeds limit repeat test with new valve, or measure stem to guide clearance as outlined in Step and to determine if wear is in the guide or the valve stem (or both)
Valve Seat Reconditioning
Valve Seat Inspection Inspect valve seat in cylinder head for pitting, burnt spots, roughness, and uneven surfaceIf any of the above conditions exist, the valve seat must be reconditionedIf the valve seat is cracked the cylinder head must be replacedToo Wide Uneven Good Too Narrow
Cylinder Head Reconditioning