2008 Polaris ATV Sportsman 300 400 H.O. Service Manual, Page 81Get this manual
ENGINE (300) Crankshaft End Play Adjustment
NOTE: The method described here is shown with the PTO main bearing on the crankshaft, which is the most common situationIf the bearing is in the case, the procedure is the same, but the photo examples will differ1Make sure all bearings are firmly seated in the crankcase3Subtract the thickness of the straightedge from the measurement obtained in Step and record
PTO Case Depth_ 4Measure the distance from the Magneto crankcase mating surface to the main bearing using the same method and recordLay straightedge on the left (PTO) crankcase and measure the distance from the straightedge to the bottom of the main bearing bore (if bearing is still on the crankshaft) or to the bearing race (if the bearing is installed in the case) using dial caliperSubtract the thickness of the straightedge from the measurement obtained in Step and record