2009-2010 Suzuki DF70A DF80A DF90A Outboard Service Manual, Page 152Get this manual
1D-41 Power Unit Mechanical: Valve spring free length Check spring strength by measuring free lengthIf lower than service limit, replace valve springSpecial tool (A): 0990020101 (Vernier calipers (150 mm)) Valve spring free length Standard (IN EX: 33.1 mm (1.30 in Service limit (IN EX 31.8 mm (1.25 in Valve spring squareness Use square and surface plate to check each spring for squareness (clearance between end of valve spring and square)If measurement exceeds service limit, replace valve springSpecial tool0990020101 (Vernier calipers (150 mm)) Valve spring squareness "a" Service limit (IN EX: 2.0 mm (0.079 in "a"