Suzuki DF9,9 Service Manual page 140

6-20 POWER UNIT
VALVE SPRING
Valve spring free length
Measure the spring free length.
 09900-20102: Vernier calipers
Standard: 32.52 mm (1.280 in)
Service limit: 32.40 mm (1.276 in)
If measurement is lower than service limit, replace valve spring.
Valve spring tension
Measure the valve spring tension.
 09900-20102: Vernier caliper
Standard: 90 N (9.0 kg, 19.8 lbs) for
28.5 mm (1.12 in)
Service limit: 76 N (7.6 kg, 16.8 lbs) for
28.5 mm (1.12 in)
If measurement is lower than service limit, replace valve spring.
OIL SEAL
Inspect condition.
If cracked, cut or damaged, replace oil seal.