Suzuki DF25/DF30 Four Stroke Service Manual, Page 150Get this manual
POWER UNIT 7-33 VALVE SPRING Valve spring free length Check spring strength by measuring free length09900-20101Vernier calipers Valve spring free length StandardINEX 47.38 mm (1.865 in Service limitINEX 45.48 mm (1.791 in If lower than service limit, replace valve spring Valve spring preload Measure valve spring preload09900-20101Vernier calipers Valve spring preload StandardINEX 193 223 (19.3 22.3 kg42.5 49.2 lbs for 37.5 mm (1.48 in ServicelimitINEX 177 (17.7 kg, 39.0 lbsfor 37.5 mm (1.48 in If lower than service limit, replace valve spring