2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 74Get this manual
ENGINE Tensioner Spring Free Length: 2.02" (5.13 cm) 4Measure free length of tensioner springReplace spring if excessively wornCompare to specifications3Measure O.Dof rocker shaftInspect it for wear or damageCompare to specificationsRocker Shaft O.D .8656-.8661" (21.987-22.0 mm) 4Measure I.Dof each rocker arm and compare to specifications
5Replace entire tensioner assembly if any part is worn or damaged
Rocker ArmShaft Inspection
5Measure I.Dof both rocker arm shaft supports and visually inspect surfaceCompare to specifications