2003 Polaris ATV Trail Boss 330 Factory Service Manual, Page 57Get this manual
ENGINE 4Measure free length of tensioner springReplace spring if excessively worn4Remove cylinder block plug using 14 mm hex head wrench
Cylinder block plug Tensioner Spring Free Length: 2.06 (5.23 cm) Std1.92 (4.88 cm) Limit 5Measure O.Dof rocker shaftInspect it for wear or damageCompare to specifications
5Replace entire tensioner assembly if any part is worn or damaged
ROCKER ARMSHAFT INSPECTION
1Remove rocker cover2Mark or tag rocker arms to keep them in order for assembly