2008 Polaris ATV Sportsman 300 400 H.O. Service Manual, Page 83Get this manual
ENGINE (300) 7Subtract the thickness of the existing shim from the result of Step to determine if different shim is neededThe result must be within the specified range listed at belowAdd or subtract shims or change shim thickness as required and install them upon assembly3Be sure balance dots on gear teeth are aligned= In mmCounter Balance Shaft End Play: .004"-.029" (.1-.74 mm)
4Apply thin coat of crankcase sealant to the outer mating surface of the left crankcaseSealant is not required on the inner mating surfaces (A)